diff --git a/Libraries/LibJS/Bytecode/PropertyAccess.h b/Libraries/LibJS/Bytecode/PropertyAccess.h
index 02036d9691..3e327fe988 100644
--- a/Libraries/LibJS/Bytecode/PropertyAccess.h
+++ b/Libraries/LibJS/Bytecode/PropertyAccess.h
@@ -401,7 +401,7 @@ inline ThrowCompletionOr<void> put_by_property_key(VM& vm, Value base, Value thi
         if (!succeeded && strict == Strict::Yes) [[unlikely]] {
             if (base.is_object())
                 return vm.throw_completion<TypeError>(ErrorType::ReferenceNullishSetProperty, name, base);
-            return vm.throw_completion<TypeError>(ErrorType::ReferencePrimitiveSetProperty, name, base.typeof_(vm)->utf8_string(), base);
+            return vm.throw_completion<TypeError>(ErrorType::ReferencePrimitiveSetProperty, name, base.typeof_(vm)->utf16_string_view().to_utf8_but_should_be_ported_to_utf16(), base);
         }
         break;
     }
diff --git a/Libraries/LibJS/Console.cpp b/Libraries/LibJS/Console.cpp
index cc9024cae0..684be9737e 100644
--- a/Libraries/LibJS/Console.cpp
+++ b/Libraries/LibJS/Console.cpp
@@ -449,7 +449,7 @@ ThrowCompletionOr<Value> Console::dirxml()
 static ThrowCompletionOr<String> label_or_fallback(VM& vm, StringView fallback)
 {
     return vm.argument_count() > 0 && !vm.argument(0).is_undefined()
-        ? vm.argument(0).to_string(vm)
+        ? TRY(vm.argument(0).to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16()
         : TRY_OR_THROW_OOM(vm, String::from_utf8(fallback));
 }
 
@@ -773,7 +773,7 @@ ThrowCompletionOr<String> Console::value_vector_to_string(GC::RootVector<Value>
         if (!builder.is_empty())
             builder.append(' ');
 
-        builder.append(TRY(item.to_string(vm)));
+        builder.append(TRY(item.to_utf16_string(vm)));
     }
 
     return MUST(builder.to_string());
@@ -832,7 +832,7 @@ ThrowCompletionOr<GC::RootVector<Value>> ConsoleClient::formatter(GC::RootVector
         return args;
 
     // 2. Let target be the first element of args.
-    auto target = (!args.is_empty()) ? TRY(args.first().to_string(vm)) : String {};
+    auto target = (!args.is_empty()) ? TRY(args.first().to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16() : String {};
 
     // 3. Let current be the second element of args.
     auto current = (args.size() > 1) ? args[1] : js_undefined();
@@ -914,13 +914,13 @@ ThrowCompletionOr<GC::RootVector<Value>> ConsoleClient::formatter(GC::RootVector
         // 6. TODO: process %c
         else if (specifier == "%c"sv) {
             // NOTE: This has no spec yet. `%c` specifiers treat the argument as CSS styling for the log message.
-            add_css_style_to_current_message(TRY(current.to_string(vm)));
+            add_css_style_to_current_message(TRY(current.to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16());
             converted = PrimitiveString::create(vm, String {});
         }
 
         // 7. If any of the previous steps set converted, replace specifier in target with converted.
         if (converted.has_value())
-            target = TRY_OR_THROW_OOM(vm, target.replace(specifier, TRY(converted->to_string(vm)), ReplaceMode::FirstOnly));
+            target = TRY_OR_THROW_OOM(vm, target.replace(specifier, TRY(converted->to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16(), ReplaceMode::FirstOnly));
     }
 
     // 7. Let result be a list containing target together with the elements of args starting from the third onward.
diff --git a/Libraries/LibJS/Contrib/Test262/262Object.cpp b/Libraries/LibJS/Contrib/Test262/262Object.cpp
index d7dfe10c12..3e6c3ca1bb 100644
--- a/Libraries/LibJS/Contrib/Test262/262Object.cpp
+++ b/Libraries/LibJS/Contrib/Test262/262Object.cpp
@@ -92,7 +92,7 @@ JS_DEFINE_NATIVE_FUNCTION($262Object::detach_array_buffer)
 
 JS_DEFINE_NATIVE_FUNCTION($262Object::eval_script)
 {
-    auto source_text = TRY(vm.argument(0).to_string(vm));
+    auto source_text = TRY(vm.argument(0).to_utf16_string(vm));
 
     // 1. Let hostDefined be any host-defined values for the provided sourceText (obtained in an implementation dependent manner)
 
@@ -100,7 +100,7 @@ JS_DEFINE_NATIVE_FUNCTION($262Object::eval_script)
     auto& realm = *vm.current_realm();
 
     // 3. Let s be ParseScript(sourceText, realm, hostDefined).
-    auto script_or_error = Script::parse(source_text, realm);
+    auto script_or_error = Script::parse(source_text.to_utf8_but_should_be_ported_to_utf16(), realm);
 
     // 4. If s is a List of errors, then
     if (script_or_error.is_error()) {
diff --git a/Libraries/LibJS/Contrib/Test262/GlobalObject.cpp b/Libraries/LibJS/Contrib/Test262/GlobalObject.cpp
index b4b099cd06..479c8587f4 100644
--- a/Libraries/LibJS/Contrib/Test262/GlobalObject.cpp
+++ b/Libraries/LibJS/Contrib/Test262/GlobalObject.cpp
@@ -36,7 +36,7 @@ void GlobalObject::visit_edges(Cell::Visitor& visitor)
 
 JS_DEFINE_NATIVE_FUNCTION(GlobalObject::print)
 {
-    auto string = TRY(vm.argument(0).to_string(vm));
+    auto string = TRY(vm.argument(0).to_utf16_string(vm));
     outln("{}", string);
     return js_undefined();
 }
diff --git a/Libraries/LibJS/Runtime/AbstractOperations.cpp b/Libraries/LibJS/Runtime/AbstractOperations.cpp
index 5e12e382de..e37ecaadb2 100644
--- a/Libraries/LibJS/Runtime/AbstractOperations.cpp
+++ b/Libraries/LibJS/Runtime/AbstractOperations.cpp
@@ -646,7 +646,7 @@ ThrowCompletionOr<Value> perform_eval(VM& vm, Value x, CallerMode strict_caller,
 
     // 6. NOTE: In the case of a direct eval, evalRealm is the realm of both the caller of eval and of the eval function itself.
     // 7. Perform ? HostEnsureCanCompileStrings(evalRealm, « », xStr, xStr, direct, « », x).
-    auto code_string_utf8 = code_string->utf8_string();
+    auto code_string_utf8 = code_string->utf16_string_view().to_utf8_but_should_be_ported_to_utf16();
     TRY(vm.host_ensure_can_compile_strings(eval_realm, {}, code_string_utf8, code_string_utf8, direct == EvalMode::Direct ? CompilationType::DirectEval : CompilationType::IndirectEval, {}, x));
 
     // 8. Let inFunction be false.
@@ -1360,8 +1360,7 @@ ThrowCompletionOr<Utf16String> get_substitution(VM& vm, Utf16View const& matched
             auto digits = template_remainder.substring_view(1, digit_count);
 
             // iii. Let index be ℝ(StringToNumber(digits)).
-            auto utf8_digits = MUST(digits.to_utf8());
-            auto index = static_cast<size_t>(string_to_number(utf8_digits));
+            auto index = static_cast<size_t>(string_to_number(digits));
 
             // iv. Assert: 0 ≤ index ≤ 99.
             VERIFY(index <= 99);
@@ -1380,8 +1379,7 @@ ThrowCompletionOr<Utf16String> get_substitution(VM& vm, Utf16View const& matched
                 digits = digits.substring_view(0, 1);
 
                 // 4. Set index to ℝ(StringToNumber(digits)).
-                utf8_digits = MUST(digits.to_utf8());
-                index = static_cast<size_t>(string_to_number(utf8_digits));
+                index = static_cast<size_t>(string_to_number(digits));
             }
 
             // vii. Let ref be the substring of templateRemainder from 0 to 1 + digitCount.
@@ -1958,8 +1956,12 @@ ThrowCompletionOr<Value> get_option(VM& vm, Object const& options, PropertyKey c
         // NOTE: Every location in the spec that invokes GetOption with type=boolean also has values=undefined.
         VERIFY(value.is_string());
 
-        if (auto value_string = value.as_string().utf8_string(); !values.contains_slow(value_string))
-            return vm.throw_completion<RangeError>(ErrorType::OptionIsNotValidValue, value_string, property.as_string());
+        auto value_string = value.as_string().utf16_string_view();
+        auto it = find_if(values.begin(), values.end(), [&](auto allowed_value) { return value_string == allowed_value; });
+        if (it == values.end())
+            return vm.throw_completion<RangeError>(ErrorType::OptionIsNotValidValue, value_string.to_utf8_but_should_be_ported_to_utf16(), property.as_string());
+
+        value = PrimitiveString::create(vm, *it);
     }
 
     // 6. Return value.
@@ -1979,7 +1981,16 @@ ThrowCompletionOr<RoundingMode> get_rounding_mode_option(VM& vm, Object const& o
     auto string_value = TRY(get_option(vm, options, vm.names.roundingMode, OptionType::String, allowed_strings, string_fallback));
 
     // 4. Return the value from the "Rounding Mode" column of the row with stringValue in its "String Identifier" column.
-    return static_cast<RoundingMode>(allowed_strings.first_index_of(string_value.as_string().utf8_string()).value());
+    auto string = string_value.as_string().utf16_string_view();
+    Optional<size_t> index;
+    for (size_t i = 0; i < allowed_strings.size(); ++i) {
+        if (string == allowed_strings[i]) {
+            index = i;
+            break;
+        }
+    }
+    VERIFY(index.has_value());
+    return static_cast<RoundingMode>(*index);
 }
 
 // 14.5.2.4 GetRoundingIncrementOption ( options ), https://tc39.es/proposal-temporal/#sec-temporal-getroundingincrementoption
diff --git a/Libraries/LibJS/Runtime/AggregateErrorConstructor.cpp b/Libraries/LibJS/Runtime/AggregateErrorConstructor.cpp
index 2829e508e0..900872637f 100644
--- a/Libraries/LibJS/Runtime/AggregateErrorConstructor.cpp
+++ b/Libraries/LibJS/Runtime/AggregateErrorConstructor.cpp
@@ -55,7 +55,7 @@ ThrowCompletionOr<GC::Ref<Object>> AggregateErrorConstructor::construct(Function
     // 3. If message is not undefined, then
     if (!message.is_undefined()) {
         // a. Let msg be ? ToString(message).
-        auto msg = TRY(message.to_string(vm));
+        auto msg = TRY(message.to_utf16_string(vm));
 
         // b. Perform CreateNonEnumerableDataPropertyOrThrow(O, "message", msg).
         aggregate_error->create_non_enumerable_data_property_or_throw(vm.names.message, PrimitiveString::create(vm, msg));
diff --git a/Libraries/LibJS/Runtime/Array.cpp b/Libraries/LibJS/Runtime/Array.cpp
index 3ead3e14d3..bc0a768372 100644
--- a/Libraries/LibJS/Runtime/Array.cpp
+++ b/Libraries/LibJS/Runtime/Array.cpp
@@ -257,10 +257,10 @@ ThrowCompletionOr<double> compare_array_elements(VM& vm, Value x, Value y, Funct
         return x.as_string().utf16_string_view() <=> y.as_string().utf16_string_view();
 
     // 5. Let xString be ? ToString(x).
-    auto x_string = PrimitiveString::create(vm, TRY(x.to_string(vm)));
+    auto x_string = PrimitiveString::create(vm, TRY(x.to_utf16_string(vm)));
 
     // 6. Let yString be ? ToString(y).
-    auto y_string = PrimitiveString::create(vm, TRY(y.to_string(vm)));
+    auto y_string = PrimitiveString::create(vm, TRY(y.to_utf16_string(vm)));
 
     // 7. Let xSmaller be ! IsLessThan(xString, yString, true).
     auto x_smaller = MUST(is_less_than(vm, x_string, y_string, true));
diff --git a/Libraries/LibJS/Runtime/Date.cpp b/Libraries/LibJS/Runtime/Date.cpp
index 322fa0c0f8..811391ab7b 100644
--- a/Libraries/LibJS/Runtime/Date.cpp
+++ b/Libraries/LibJS/Runtime/Date.cpp
@@ -8,6 +8,7 @@
 #include <AK/NeverDestroyed.h>
 #include <AK/NumericLimits.h>
 #include <AK/Time.h>
+#include <AK/Utf16String.h>
 #include <AK/Utf16StringBuilder.h>
 #include <LibJS/Runtime/AbstractOperations.h>
 #include <LibJS/Runtime/Date.h>
@@ -664,7 +665,8 @@ double time_clip(double time)
 bool is_offset_time_zone_identifier(StringView offset_string)
 {
     // 1. Let parseResult be ParseText(StringToCodePoints(offsetString), UTCOffset[~SubMinutePrecision]).
-    auto parse_result = Temporal::parse_utc_offset(offset_string, Temporal::SubMinutePrecision::No);
+    auto utf16_offset_string = Utf16String::from_utf8(offset_string);
+    auto parse_result = Temporal::parse_utc_offset(utf16_offset_string, Temporal::SubMinutePrecision::No);
 
     // 2. If parseResult is a List of errors, return false.
     // 3. Return true.
@@ -676,7 +678,8 @@ bool is_offset_time_zone_identifier(StringView offset_string)
 ThrowCompletionOr<double> parse_date_time_utc_offset(VM& vm, StringView offset_string)
 {
     // 1. Let parseResult be ParseText(offsetString, UTCOffset[+SubMinutePrecision]).
-    auto parse_result = Temporal::parse_utc_offset(offset_string, Temporal::SubMinutePrecision::Yes);
+    auto utf16_offset_string = Utf16String::from_utf8(offset_string);
+    auto parse_result = Temporal::parse_utc_offset(utf16_offset_string, Temporal::SubMinutePrecision::Yes);
 
     // 2. If parseResult is a List of errors, throw a RangeError exception.
     if (!parse_result.has_value())
@@ -692,7 +695,8 @@ double parse_date_time_utc_offset(StringView offset_string)
     // OPTIMIZATION: Some callers can assume that parsing will succeed.
 
     // 1. Let parseResult be ParseText(offsetString, UTCOffset[+SubMinutePrecision]).
-    auto parse_result = Temporal::parse_utc_offset(offset_string, Temporal::SubMinutePrecision::Yes);
+    auto utf16_offset_string = Utf16String::from_utf8(offset_string);
+    auto parse_result = Temporal::parse_utc_offset(utf16_offset_string, Temporal::SubMinutePrecision::Yes);
     VERIFY(parse_result.has_value());
 
     return parse_date_time_utc_offset(*parse_result);
@@ -751,13 +755,13 @@ double parse_date_time_utc_offset(Temporal::TimeZoneOffset const& parse_result)
         auto parsed_fraction = *parse_result.fraction;
 
         // b. Let fraction be the string-concatenation of CodePointsToString(parsedFraction) and "000000000".
-        auto fraction = ByteString::formatted("{}000000000", parsed_fraction);
-
         // c. Let nanosecondsString be the substring of fraction from 1 to 10.
-        auto nanoseconds_string = fraction.substring_view(1, 9);
-
         // d. Let nanoseconds be ℝ(StringToNumber(nanosecondsString)).
-        nanoseconds = string_to_number(nanoseconds_string);
+        for (size_t i = 1; i < 10; ++i) {
+            nanoseconds *= 10;
+            if (i < parsed_fraction.length_in_code_units())
+                nanoseconds += parse_ascii_digit(static_cast<char>(parsed_fraction.code_unit_at(i)));
+        }
     }
 
     // 17. Return sign × (((hours × 60 + minutes) × 60 + seconds) × 10^9 + nanoseconds).
diff --git a/Libraries/LibJS/Runtime/DateConstructor.cpp b/Libraries/LibJS/Runtime/DateConstructor.cpp
index 901fe7bf8d..14f0d5bb87 100644
--- a/Libraries/LibJS/Runtime/DateConstructor.cpp
+++ b/Libraries/LibJS/Runtime/DateConstructor.cpp
@@ -9,6 +9,7 @@
  */
 
 #include <AK/Time.h>
+#include <AK/Utf16View.h>
 #include <LibJS/Runtime/AbstractOperations.h>
 #include <LibJS/Runtime/Date.h>
 #include <LibJS/Runtime/DateConstructor.h>
@@ -32,6 +33,12 @@ static double parse_date_string(VM& vm, StringView date_string)
     return result;
 }
 
+static double parse_date_string(VM& vm, Utf16View date_string)
+{
+    auto utf8_date_string = date_string.to_utf8_but_should_be_ported_to_utf16();
+    return parse_date_string(vm, utf8_date_string.bytes_as_string_view());
+}
+
 DateConstructor::DateConstructor(Realm& realm)
     : NativeFunction(realm.vm().names.Date.as_string(), realm.intrinsics().function_prototype())
 {
@@ -97,7 +104,7 @@ ThrowCompletionOr<GC::Ref<Object>> DateConstructor::construct(FunctionObject& ne
             if (primitive.is_string()) {
                 // 1. Assert: The next step never returns an abrupt completion because Type(v) is String.
                 // 2. Let tv be the result of parsing v as a date, in exactly the same manner as for the parse method (21.4.3.2).
-                time_value = parse_date_string(vm, primitive.as_string().utf8_string());
+                time_value = parse_date_string(vm, primitive.as_string().utf16_string_view());
             }
             // iii. Else,
             else {
@@ -174,7 +181,7 @@ JS_DEFINE_NATIVE_FUNCTION(DateConstructor::parse)
 
     // This function applies the ToString operator to its argument. If ToString results in an abrupt completion the
     // Completion Record is immediately returned.
-    auto date_string = TRY(vm.argument(0).to_string(vm));
+    auto date_string = TRY(vm.argument(0).to_utf16_string(vm));
 
     // Otherwise, this function interprets the resulting String as a date and time; it returns a Number, the UTC time
     // value corresponding to the date and time.
diff --git a/Libraries/LibJS/Runtime/ErrorPrototype.cpp b/Libraries/LibJS/Runtime/ErrorPrototype.cpp
index fc0baed0f3..040a4580a9 100644
--- a/Libraries/LibJS/Runtime/ErrorPrototype.cpp
+++ b/Libraries/LibJS/Runtime/ErrorPrototype.cpp
@@ -47,8 +47,8 @@ JS_DEFINE_NATIVE_FUNCTION(ErrorPrototype::to_string)
 
     // 4. If name is undefined, set name to "Error"; otherwise set name to ? ToString(name).
     auto name = name_property.is_undefined()
-        ? "Error"_string
-        : TRY(name_property.to_string(vm));
+        ? "Error"_utf16
+        : TRY(name_property.to_utf16_string(vm));
 
     // 5. Let msg be ? Get(O, "message").
     auto message_property = TRY(this_object->get(vm.names.message));
@@ -67,7 +67,7 @@ JS_DEFINE_NATIVE_FUNCTION(ErrorPrototype::to_string)
         return PrimitiveString::create(vm, move(name));
 
     // 9. Return the string-concatenation of name, the code unit 0x003A (COLON), the code unit 0x0020 (SPACE), and msg.
-    return PrimitiveString::create(vm, MUST(String::formatted("{}: {}", name, message)));
+    return PrimitiveString::create(vm, Utf16String::formatted("{}: {}", name, message));
 }
 
 // B.1.1 get Error.prototype.stack ( ), https://tc39.es/proposal-error-stacks/#sec-get-error.prototype-stack
@@ -91,11 +91,11 @@ JS_DEFINE_NATIVE_FUNCTION(ErrorPrototype::stack_getter)
     // 4. Return ? GetStackString(error).
     // NOTE: These steps are not implemented based on the proposal, but to roughly follow behavior of other browsers.
 
-    String name {};
+    Utf16String name {};
     if (auto name_property = TRY(this_object->get(vm.names.name)); !name_property.is_undefined())
-        name = TRY(name_property.to_string(vm));
+        name = TRY(name_property.to_utf16_string(vm));
     else
-        name = "Error"_string;
+        name = "Error"_utf16;
 
     Utf16String message {};
     if (auto message_property = TRY(this_object->get(vm.names.message)); !message_property.is_undefined())
@@ -103,7 +103,7 @@ JS_DEFINE_NATIVE_FUNCTION(ErrorPrototype::stack_getter)
 
     auto header = message.is_empty()
         ? move(name)
-        : MUST(String::formatted("{}: {}", name, message));
+        : Utf16String::formatted("{}: {}", name, message);
 
     auto string = PrimitiveString::create(vm, Utf16String::formatted("{}\n{}", header, error_data->stack_string()));
     error_data->set_cached_string(string);
diff --git a/Libraries/LibJS/Runtime/FunctionConstructor.cpp b/Libraries/LibJS/Runtime/FunctionConstructor.cpp
index 3542933fdb..f772934441 100644
--- a/Libraries/LibJS/Runtime/FunctionConstructor.cpp
+++ b/Libraries/LibJS/Runtime/FunctionConstructor.cpp
@@ -115,11 +115,11 @@ ThrowCompletionOr<GC::Ref<ECMAScriptFunctionObject>> FunctionConstructor::create
     // 8. For each element arg of parameterArgs, do
     for (auto const& parameter_value : parameter_args) {
         // a. Append ? ToString(arg) to parameterStrings.
-        parameter_strings.unchecked_append(TRY(parameter_value.to_string(vm)));
+        parameter_strings.unchecked_append(TRY(parameter_value.to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16());
     }
 
     // 9. Let bodyString be ? ToString(bodyArg).
-    auto body_string = TRY(body_arg.to_string(vm));
+    auto body_string = TRY(body_arg.to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16();
 
     // 10. Let currentRealm be the current Realm Record.
     auto& realm = *vm.current_realm();
diff --git a/Libraries/LibJS/Runtime/GlobalObject.cpp b/Libraries/LibJS/Runtime/GlobalObject.cpp
index 30eec103d1..85766eac4f 100644
--- a/Libraries/LibJS/Runtime/GlobalObject.cpp
+++ b/Libraries/LibJS/Runtime/GlobalObject.cpp
@@ -237,7 +237,7 @@ JS_DEFINE_NATIVE_FUNCTION(GlobalObject::parse_float)
     }
 
     // 1. Let inputString be ? ToString(string).
-    auto input_string = TRY(string.to_string(vm));
+    auto input_string = TRY(string.to_utf16_string(vm));
 
     // 2. Let trimmedString be ! TrimString(inputString, start).
     auto trimmed_string = MUST(trim_string(vm, PrimitiveString::create(vm, move(input_string)), TrimMode::Left));
@@ -249,17 +249,17 @@ JS_DEFINE_NATIVE_FUNCTION(GlobalObject::parse_float)
     // 5. Let parsedNumber be ParseText(StringToCodePoints(numberString), StrDecimalLiteral).
     // 6. Assert: parsedNumber is a Parse Node.
     // 7. Return StringNumericValue of parsedNumber.
-    auto trimmed_string_view = trimmed_string.bytes_as_string_view();
+    auto trimmed_string_view = trimmed_string.utf16_view();
 
     auto parsed_number = AK::parse_first_number<double>(trimmed_string_view, TrimWhitespace::No);
     if (parsed_number.has_value())
         return parsed_number->value;
 
-    auto first_code_point = *trimmed_string.code_points().begin();
+    auto first_code_point = *trimmed_string.begin();
     if (first_code_point == '-' || first_code_point == '+')
         trimmed_string_view = trimmed_string_view.substring_view(1);
 
-    if (trimmed_string_view.starts_with("Infinity"sv, AK::CaseSensitivity::CaseSensitive)) {
+    if (trimmed_string_view.starts_with("Infinity"sv)) {
         // Only an immediate - means we should return negative infinity
         return first_code_point == '-' ? js_negative_infinity() : js_infinity();
     }
@@ -273,12 +273,12 @@ JS_DEFINE_NATIVE_FUNCTION(GlobalObject::parse_int)
     auto string = vm.argument(0);
 
     // 1. Let inputString be ? ToString(string).
-    auto input_string = TRY(string.to_string(vm));
+    auto input_string = TRY(string.to_utf16_string(vm));
 
     // 2. Let S be ! TrimString(inputString, start).
-    String trimmed_string;
+    Utf16String trimmed_string;
     // OPTIMIZATION: We can skip the trimming step when the value already starts with an alphanumeric ASCII character.
-    if (input_string.is_empty() || is_ascii_alphanumeric(input_string.bytes_as_string_view()[0])) {
+    if (input_string.is_empty() || is_ascii_alphanumeric(input_string.code_unit_at(0))) {
         trimmed_string = input_string;
     } else {
         trimmed_string = MUST(trim_string(vm, PrimitiveString::create(vm, move(input_string)), TrimMode::Left));
@@ -288,12 +288,12 @@ JS_DEFINE_NATIVE_FUNCTION(GlobalObject::parse_int)
     auto sign = 1;
 
     // 4. If S is not empty and the first code unit of S is the code unit 0x002D (HYPHEN-MINUS), set sign to -1.
-    auto first_code_point = trimmed_string.is_empty() ? OptionalNone {} : Optional<u32> { *trimmed_string.code_points().begin() };
+    auto first_code_point = trimmed_string.is_empty() ? OptionalNone {} : Optional<u32> { *trimmed_string.begin() };
     if (first_code_point == 0x2Du)
         sign = -1;
 
     // 5. If S is not empty and the first code unit of S is the code unit 0x002B (PLUS SIGN) or the code unit 0x002D (HYPHEN-MINUS), remove the first code unit from S.
-    auto trimmed_view = trimmed_string.bytes_as_string_view();
+    auto trimmed_view = trimmed_string.utf16_view();
     if (first_code_point == 0x2Bu || first_code_point == 0x2Du)
         trimmed_view = trimmed_view.substring_view(1);
 
@@ -322,7 +322,7 @@ JS_DEFINE_NATIVE_FUNCTION(GlobalObject::parse_int)
     // 10. If stripPrefix is true, then
     if (strip_prefix) {
         // a. If the length of S is at least 2 and the first two code units of S are either "0x" or "0X", then
-        if (trimmed_view.length() >= 2 && trimmed_view.substring_view(0, 2).equals_ignoring_ascii_case("0x"sv)) {
+        if (trimmed_view.length_in_code_units() >= 2 && trimmed_view.substring_view(0, 2).equals_ignoring_ascii_case("0x"sv)) {
             // i. Remove the first two code units from S.
             trimmed_view = trimmed_view.substring_view(2);
 
@@ -346,7 +346,7 @@ JS_DEFINE_NATIVE_FUNCTION(GlobalObject::parse_int)
 
     bool had_digits = false;
     double number = 0;
-    for (auto code_point : Utf8View(trimmed_view)) {
+    for (auto code_point : trimmed_view) {
         auto digit = parse_digit(code_point);
         if (!digit.has_value())
             break;
diff --git a/Libraries/LibJS/Runtime/Intl/AbstractOperations.cpp b/Libraries/LibJS/Runtime/Intl/AbstractOperations.cpp
index 2ddded130e..b0dcdc8ef6 100644
--- a/Libraries/LibJS/Runtime/Intl/AbstractOperations.cpp
+++ b/Libraries/LibJS/Runtime/Intl/AbstractOperations.cpp
@@ -307,7 +307,7 @@ ThrowCompletionOr<Vector<String>> canonicalize_locale_list(VM& vm, Value locales
             // iv. Else,
             else {
                 // 1. Let tag be ? ToString(kValue).
-                tag = TRY(key_value.to_string(vm));
+                tag = TRY(key_value.to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16();
             }
 
             // v. If IsWellFormedLanguageTag(tag) is false, throw a RangeError exception.
@@ -451,7 +451,7 @@ ResolvedLocale resolve_locale(ReadonlySpan<String> requested_locales, LocaleOpti
     Optional<MatchedLocale> matcher_result;
 
     // 2. If matcher is "lookup", then
-    if (matcher.is_string() && matcher.as_string().utf8_string() == "lookup"sv) {
+    if (matcher.is_string() && matcher.as_string().utf16_string_view() == "lookup"sv) {
         // a. Let r be LookupMatchingLocaleByPrefix(availableLocales, requestedLocales).
         matcher_result = lookup_matching_locale_by_prefix(requested_locales);
     }
@@ -639,7 +639,7 @@ ThrowCompletionOr<ResolvedOptions> resolve_options(VM& vm, IntlObject& object, V
         // d. If value is not undefined, then
         if (!value.is_undefined()) {
             // i. Set value to ! ToString(value).
-            auto value_string = MUST(value.to_string(vm));
+            auto value_string = MUST(value.to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16();
 
             // ii. If value cannot be matched by the type Unicode locale nonterminal, throw a RangeError exception.
             if (!Unicode::is_type_identifier(value_string))
@@ -688,7 +688,7 @@ ThrowCompletionOr<GC::Ref<Array>> filter_locales(VM& vm, ReadonlySpan<String> re
         Optional<MatchedLocale> match;
 
         // a. If matcher is "lookup", then
-        if (matcher.as_string().utf8_string() == "lookup"sv) {
+        if (matcher.as_string().utf16_string_view() == "lookup"sv) {
             // i. Let match be LookupMatchingLocaleByPrefix(availableLocales, « locale »).
             match = lookup_matching_locale_by_prefix({ { locale } });
         }
@@ -743,12 +743,13 @@ ThrowCompletionOr<StringOrBoolean> get_boolean_or_string_number_format_option(VM
         return StringOrBoolean { false };
 
     // 5. Let value be ? ToString(value).
-    auto value_string = TRY(value.to_string(vm));
+    auto value_string = TRY(value.to_utf16_string(vm));
 
     // 6. If stringValues does not contain value, throw a RangeError exception.
-    auto it = find(string_values.begin(), string_values.end(), value_string.bytes_as_string_view());
+    auto value_string_view = value_string.utf16_view();
+    auto it = find_if(string_values.begin(), string_values.end(), [&](auto allowed_value) { return value_string_view == allowed_value; });
     if (it == string_values.end())
-        return vm.throw_completion<RangeError>(ErrorType::OptionIsNotValidValue, value_string, property.as_string());
+        return vm.throw_completion<RangeError>(ErrorType::OptionIsNotValidValue, value_string_view.to_utf8_but_should_be_ported_to_utf16(), property.as_string());
 
     // 7. Return value.
     return StringOrBoolean { *it };
diff --git a/Libraries/LibJS/Runtime/Intl/CollatorConstructor.cpp b/Libraries/LibJS/Runtime/Intl/CollatorConstructor.cpp
index 9e5f217ff0..1ed97a853a 100644
--- a/Libraries/LibJS/Runtime/Intl/CollatorConstructor.cpp
+++ b/Libraries/LibJS/Runtime/Intl/CollatorConstructor.cpp
@@ -69,7 +69,7 @@ ThrowCompletionOr<GC::Ref<Object>> CollatorConstructor::construct(FunctionObject
     auto usage = TRY(get_option(vm, options, vm.names.usage, OptionType::String, { "sort"sv, "search"sv }, "sort"sv));
 
     // 8. Set collator.[[Usage]] to usage.
-    collator->set_usage(usage.as_string().utf8_string());
+    collator->set_usage(usage.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16());
 
     // 9. If usage is "sort", then
     //     a. Let localeData be %Intl.Collator%.[[SortLocaleData]].
@@ -113,7 +113,7 @@ ThrowCompletionOr<GC::Ref<Object>> CollatorConstructor::construct(FunctionObject
 
     Optional<Unicode::Sensitivity> sensitivity;
     if (!sensitivity_value.is_undefined())
-        sensitivity = Unicode::sensitivity_from_string(sensitivity_value.as_string().utf8_string());
+        sensitivity = Unicode::sensitivity_from_string(sensitivity_value.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16());
 
     // 21. Let defaultIgnorePunctuation be resolvedLocaleData.[[ignorePunctuation]].
     // NOTE: We do not acquire resolvedLocaleData.[[ignorePunctuation]] here. Instead, we let LibUnicode fill in the
diff --git a/Libraries/LibJS/Runtime/Intl/DateTimeFormatConstructor.cpp b/Libraries/LibJS/Runtime/Intl/DateTimeFormatConstructor.cpp
index 3f72a29e99..849abb22bc 100644
--- a/Libraries/LibJS/Runtime/Intl/DateTimeFormatConstructor.cpp
+++ b/Libraries/LibJS/Runtime/Intl/DateTimeFormatConstructor.cpp
@@ -4,6 +4,7 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <AK/Utf16String.h>
 #include <LibJS/Runtime/AbstractOperations.h>
 #include <LibJS/Runtime/Array.h>
 #include <LibJS/Runtime/Date.h>
@@ -191,7 +192,7 @@ ThrowCompletionOr<GC::Ref<DateTimeFormat>> create_date_time_format(VM& vm, Funct
             return vm.throw_completion<TypeError>(ErrorType::IntlInvalidDateTimeFormatOption, vm.names.timeZone, "a toLocaleString time zone"sv);
 
         // b. Set timeZone to ? ToString(timeZone).
-        time_zone = TRY(time_zone_value.to_string(vm));
+        time_zone = TRY(time_zone_value.to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16();
     }
 
     // 20. If IsTimeZoneOffsetString(timeZone) is true, then
@@ -199,7 +200,8 @@ ThrowCompletionOr<GC::Ref<DateTimeFormat>> create_date_time_format(VM& vm, Funct
 
     if (is_time_zone_offset_string) {
         // a. Let parseResult be ParseText(StringToCodePoints(timeZone), UTCOffset[~SubMinutePrecision]).
-        auto parse_result = Temporal::parse_utc_offset(time_zone, Temporal::SubMinutePrecision::No);
+        auto utf16_time_zone = Utf16String::from_utf8(time_zone);
+        auto parse_result = Temporal::parse_utc_offset(utf16_time_zone, Temporal::SubMinutePrecision::No);
 
         // b. Assert: parseResult is a Parse Node.
         VERIFY(parse_result.has_value());
@@ -275,7 +277,7 @@ ThrowCompletionOr<GC::Ref<DateTimeFormat>> create_date_time_format(VM& vm, Funct
 
             // d. Set formatOptions.[[<prop>]] to value.
             if (!value.is_undefined()) {
-                option = Unicode::calendar_pattern_style_from_string(value.as_string().utf8_string());
+                option = Unicode::calendar_pattern_style_from_string(value.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16());
 
                 // e. If value is not undefined, then
                 //     i. Set hasExplicitFormatComponents to true.
@@ -294,14 +296,14 @@ ThrowCompletionOr<GC::Ref<DateTimeFormat>> create_date_time_format(VM& vm, Funct
 
     // 29. Set dateTimeFormat.[[DateStyle]] to dateStyle.
     if (!date_style.is_undefined())
-        date_time_format->set_date_style(date_style.as_string().utf8_string());
+        date_time_format->set_date_style(date_style.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16());
 
     // 30. Let timeStyle be ? GetOption(options, "timeStyle", string, « "full", "long", "medium", "short" », undefined).
     auto time_style = TRY(get_option(vm, *options, vm.names.timeStyle, OptionType::String, AK::Array { "full"sv, "long"sv, "medium"sv, "short"sv }, Empty {}));
 
     // 31. Set dateTimeFormat.[[TimeStyle]] to timeStyle.
     if (!time_style.is_undefined())
-        date_time_format->set_time_style(time_style.as_string().utf8_string());
+        date_time_format->set_time_style(time_style.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16());
 
     // 32. Let formats be resolvedLocaleData.[[formats]].[[<resolvedCalendar>]].
 
diff --git a/Libraries/LibJS/Runtime/Intl/DisplayNamesConstructor.cpp b/Libraries/LibJS/Runtime/Intl/DisplayNamesConstructor.cpp
index b4309085cf..7e8d7ebf1e 100644
--- a/Libraries/LibJS/Runtime/Intl/DisplayNamesConstructor.cpp
+++ b/Libraries/LibJS/Runtime/Intl/DisplayNamesConstructor.cpp
@@ -64,7 +64,7 @@ ThrowCompletionOr<GC::Ref<Object>> DisplayNamesConstructor::construct(FunctionOb
     auto style = TRY(get_option(vm, *options, vm.names.style, OptionType::String, { "narrow"sv, "short"sv, "long"sv }, "long"sv));
 
     // 7. Set displayNames.[[Style]] to style.
-    display_names->set_style(style.as_string().utf8_string());
+    display_names->set_style(style.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16());
 
     // 8. Let type be ? GetOption(options, "type", string, « "language", "region", "script", "currency", "calendar", "dateTimeField" », undefined).
     auto type = TRY(get_option(vm, *options, vm.names.type, OptionType::String, { "language"sv, "region"sv, "script"sv, "currency"sv, "calendar"sv, "dateTimeField"sv }, Empty {}));
@@ -74,13 +74,13 @@ ThrowCompletionOr<GC::Ref<Object>> DisplayNamesConstructor::construct(FunctionOb
         return vm.throw_completion<TypeError>(ErrorType::IsUndefined, "options.type"sv);
 
     // 10. Set displayNames.[[Type]] to type.
-    display_names->set_type(type.as_string().utf8_string());
+    display_names->set_type(type.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16());
 
     // 11. Let fallback be ? GetOption(options, "fallback", string, « "code", "none" », "code").
     auto fallback = TRY(get_option(vm, *options, vm.names.fallback, OptionType::String, { "code"sv, "none"sv }, "code"sv));
 
     // 12. Set displayNames.[[Fallback]] to fallback.
-    display_names->set_fallback(fallback.as_string().utf8_string());
+    display_names->set_fallback(fallback.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16());
 
     // 13. Set displayNames.[[Locale]] to r.[[Locale]].
     display_names->set_locale(move(result.locale));
@@ -98,7 +98,7 @@ ThrowCompletionOr<GC::Ref<Object>> DisplayNamesConstructor::construct(FunctionOb
     // 20. If type is "language", then
     if (display_names->type() == DisplayNames::Type::Language) {
         // a. Set displayNames.[[LanguageDisplay]] to languageDisplay.
-        display_names->set_language_display(language_display.as_string().utf8_string());
+        display_names->set_language_display(language_display.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16());
 
         // b. Set typeFields to typeFields.[[<languageDisplay>]].
         // c. Assert: typeFields is a Record (see 12.2.3).
diff --git a/Libraries/LibJS/Runtime/Intl/DisplayNamesPrototype.cpp b/Libraries/LibJS/Runtime/Intl/DisplayNamesPrototype.cpp
index a5e8dcf7fa..fafe52c10b 100644
--- a/Libraries/LibJS/Runtime/Intl/DisplayNamesPrototype.cpp
+++ b/Libraries/LibJS/Runtime/Intl/DisplayNamesPrototype.cpp
@@ -74,11 +74,11 @@ JS_DEFINE_NATIVE_FUNCTION(DisplayNamesPrototype::of)
     auto display_names = TRY(typed_this_object(vm));
 
     // 3. Let code be ? ToString(code).
-    code = PrimitiveString::create(vm, TRY(code.to_string(vm)));
+    code = PrimitiveString::create(vm, TRY(code.to_utf16_string(vm)));
 
     // 4. Let code be ? CanonicalCodeForDisplayNames(displayNames.[[Type]], code).
-    code = TRY(canonical_code_for_display_names(vm, display_names->type(), code.as_string().utf8_string()));
-    auto code_string = code.as_string().utf8_string();
+    code = TRY(canonical_code_for_display_names(vm, display_names->type(), code.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16()));
+    auto code_string = code.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16();
 
     // 5. Let fields be displayNames.[[Fields]].
     // 6. If fields has a field [[<code>]], return fields.[[<code>]].
diff --git a/Libraries/LibJS/Runtime/Intl/DurationFormat.cpp b/Libraries/LibJS/Runtime/Intl/DurationFormat.cpp
index 63587cb8e0..8c25c1f1b5 100644
--- a/Libraries/LibJS/Runtime/Intl/DurationFormat.cpp
+++ b/Libraries/LibJS/Runtime/Intl/DurationFormat.cpp
@@ -269,7 +269,7 @@ ThrowCompletionOr<DurationFormat::DurationUnitOptions> get_duration_unit_options
             display_default = "auto"sv;
         }
     } else {
-        style = DurationFormat::value_style_from_string(style_value.as_string().utf8_string());
+        style = DurationFormat::value_style_from_string(style_value.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16());
     }
 
     // 4. If style is "numeric" and IsFractionalSecondUnitName(unit) is true, then
@@ -286,7 +286,7 @@ ThrowCompletionOr<DurationFormat::DurationUnitOptions> get_duration_unit_options
 
     // 6. Let display be ? GetOption(options, displayField, STRING, « "auto", "always" », displayDefault).
     auto display_value = TRY(get_option(vm, options, display_field, OptionType::String, { "auto"sv, "always"sv }, display_default));
-    auto display = DurationFormat::display_from_string(display_value.as_string().utf8_string());
+    auto display = DurationFormat::display_from_string(display_value.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16());
 
     // 7. Perform ? ValidateDurationUnitStyle(unit, style, display, prevStyle).
     TRY(validate_duration_unit_style(vm, unit_property_key, style, display, previous_style, display_field));
diff --git a/Libraries/LibJS/Runtime/Intl/DurationFormatConstructor.cpp b/Libraries/LibJS/Runtime/Intl/DurationFormatConstructor.cpp
index 5afe13e373..c8ae799b1d 100644
--- a/Libraries/LibJS/Runtime/Intl/DurationFormatConstructor.cpp
+++ b/Libraries/LibJS/Runtime/Intl/DurationFormatConstructor.cpp
@@ -83,7 +83,7 @@ ThrowCompletionOr<GC::Ref<Object>> DurationFormatConstructor::construct(Function
     auto style = TRY(get_option(vm, *options, vm.names.style, OptionType::String, { "long"sv, "short"sv, "narrow"sv, "digital"sv }, "short"sv));
 
     // 13. Set durationFormat.[[Style]] to style.
-    duration_format->set_style(style.as_string().utf8_string());
+    duration_format->set_style(style.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16());
 
     // 14. Let prevStyle be the empty String.
     Optional<DurationFormat::ValueStyle> previous_style;
diff --git a/Libraries/LibJS/Runtime/Intl/Intl.cpp b/Libraries/LibJS/Runtime/Intl/Intl.cpp
index e8b3c073f5..58ab214c26 100644
--- a/Libraries/LibJS/Runtime/Intl/Intl.cpp
+++ b/Libraries/LibJS/Runtime/Intl/Intl.cpp
@@ -111,7 +111,7 @@ JS_DEFINE_NATIVE_FUNCTION(Intl::supported_values_of)
     auto& realm = *vm.current_realm();
 
     // 1. Let key be ? ToString(key).
-    auto key = TRY(vm.argument(0).to_string(vm));
+    auto key = TRY(vm.argument(0).to_utf16_string(vm));
 
     Optional<Variant<ReadonlySpan<StringView>, ReadonlySpan<String>>> list;
 
diff --git a/Libraries/LibJS/Runtime/Intl/ListFormatConstructor.cpp b/Libraries/LibJS/Runtime/Intl/ListFormatConstructor.cpp
index 1d229c934a..d15de16036 100644
--- a/Libraries/LibJS/Runtime/Intl/ListFormatConstructor.cpp
+++ b/Libraries/LibJS/Runtime/Intl/ListFormatConstructor.cpp
@@ -66,13 +66,13 @@ ThrowCompletionOr<GC::Ref<Object>> ListFormatConstructor::construct(FunctionObje
     auto type = TRY(get_option(vm, *options, vm.names.type, OptionType::String, { "conjunction"sv, "disjunction"sv, "unit"sv }, "conjunction"sv));
 
     // 8. Set listFormat.[[Type]] to type.
-    list_format->set_type(type.as_string().utf8_string());
+    list_format->set_type(type.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16());
 
     // 9. Let style be ? GetOption(options, "style", string, « "long", "short", "narrow" », "long").
     auto style = TRY(get_option(vm, *options, vm.names.style, OptionType::String, { "long"sv, "short"sv, "narrow"sv }, "long"sv));
 
     // 10. Set listFormat.[[Style]] to style.
-    list_format->set_style(style.as_string().utf8_string());
+    list_format->set_style(style.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16());
 
     // 11. Let resolvedLocaleData be r.[[LocaleData]].
     // 12. Let dataLocaleTypes be resolvedLocaleData.[[<type>]].
diff --git a/Libraries/LibJS/Runtime/Intl/LocaleConstructor.cpp b/Libraries/LibJS/Runtime/Intl/LocaleConstructor.cpp
index cf6f0ec338..cd4d5d4ac6 100644
--- a/Libraries/LibJS/Runtime/Intl/LocaleConstructor.cpp
+++ b/Libraries/LibJS/Runtime/Intl/LocaleConstructor.cpp
@@ -37,10 +37,10 @@ static ThrowCompletionOr<Optional<String>> get_string_option(VM& vm, Object cons
     if (option.is_undefined())
         return OptionalNone {};
 
-    if (validator && !validator(option.as_string().utf8_string()))
+    if (validator && !validator(option.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16()))
         return vm.throw_completion<RangeError>(ErrorType::OptionIsNotValidValue, option, property);
 
-    return option.as_string().utf8_string();
+    return option.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16();
 }
 
 // 15.1.2 UpdateLanguageId ( tag, options ), https://tc39.es/ecma402/#sec-updatelanguageid
@@ -286,7 +286,7 @@ ThrowCompletionOr<GC::Ref<Object>> LocaleConstructor::construct(FunctionObject&
             return locale_tag->locale();
         // 9. Else,
         //     a. Let tag be ? ToString(tag).
-        return tag_value.to_string(vm);
+        return TRY(tag_value.to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16();
     }());
 
     // 10. Set options to ? CoerceOptionsToObject(options).
@@ -351,7 +351,7 @@ ThrowCompletionOr<GC::Ref<Object>> LocaleConstructor::construct(FunctionObject&
     // 30. If kn is not undefined, set kn to ! ToString(kn).
     // 31. Set opt.[[kn]] to kn.
     if (!kn.is_undefined())
-        opt.kn = TRY(kn.to_string(vm));
+        opt.kn = TRY(kn.to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16();
 
     // 32. Let numberingSystem be ? GetOption(options, "numberingSystem", STRING, EMPTY, undefined).
     // 33. If numberingSystem is not undefined, then
diff --git a/Libraries/LibJS/Runtime/Intl/NumberFormat.cpp b/Libraries/LibJS/Runtime/Intl/NumberFormat.cpp
index fc8c4b850b..3fe3c9a2ed 100644
--- a/Libraries/LibJS/Runtime/Intl/NumberFormat.cpp
+++ b/Libraries/LibJS/Runtime/Intl/NumberFormat.cpp
@@ -222,7 +222,7 @@ ThrowCompletionOr<MathematicalValue> to_intl_mathematical_value(VM& vm, Value va
 
     // 3. If Type(primValue) is String,
     // a.     Let str be primValue.
-    auto string = primitive_value.as_string().utf8_string();
+    auto string = primitive_value.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16();
 
     // Step 4 handled separately by the FIXME above.
 
diff --git a/Libraries/LibJS/Runtime/Intl/NumberFormatConstructor.cpp b/Libraries/LibJS/Runtime/Intl/NumberFormatConstructor.cpp
index 4e8103106e..e54efad7c9 100644
--- a/Libraries/LibJS/Runtime/Intl/NumberFormatConstructor.cpp
+++ b/Libraries/LibJS/Runtime/Intl/NumberFormatConstructor.cpp
@@ -78,7 +78,7 @@ ThrowCompletionOr<GC::Ref<Object>> NumberFormatConstructor::construct(FunctionOb
     auto notation = TRY(get_option(vm, *options, vm.names.notation, OptionType::String, { "standard"sv, "scientific"sv, "engineering"sv, "compact"sv }, "standard"sv));
 
     // 12. Set numberFormat.[[Notation]] to notation.
-    number_format->set_notation(notation.as_string().utf8_string());
+    number_format->set_notation(notation.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16());
 
     int default_min_fraction_digits = 0;
     int default_max_fraction_digits = 0;
@@ -121,7 +121,7 @@ ThrowCompletionOr<GC::Ref<Object>> NumberFormatConstructor::construct(FunctionOb
     // 18. If notation is "compact", then
     if (number_format->notation() == Unicode::Notation::Compact) {
         // a. Set numberFormat.[[CompactDisplay]] to compactDisplay.
-        number_format->set_compact_display(compact_display.as_string().utf8_string());
+        number_format->set_compact_display(compact_display.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16());
 
         // b. Set defaultUseGrouping to "min2".
         default_use_grouping = "min2"sv;
@@ -150,7 +150,7 @@ ThrowCompletionOr<GC::Ref<Object>> NumberFormatConstructor::construct(FunctionOb
     auto sign_display = TRY(get_option(vm, *options, vm.names.signDisplay, OptionType::String, { "auto"sv, "never"sv, "always"sv, "exceptZero"sv, "negative"sv }, "auto"sv));
 
     // 25. Set numberFormat.[[SignDisplay]] to signDisplay.
-    number_format->set_sign_display(sign_display.as_string().utf8_string());
+    number_format->set_sign_display(sign_display.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16());
 
     // 26. If the implementation supports the normative optional constructor mode of 4.3 Note 1, then
     //     a. Let this be the this value.
@@ -202,7 +202,7 @@ ThrowCompletionOr<void> set_number_format_digit_options(VM& vm, NumberFormatBase
 
     // 10. Let roundingPriority be ? GetOption(options, "roundingPriority", STRING, « "auto", "morePrecision", "lessPrecision" », "auto").
     auto rounding_priority_option = TRY(get_option(vm, options, vm.names.roundingPriority, OptionType::String, { "auto"sv, "morePrecision"sv, "lessPrecision"sv }, "auto"sv));
-    auto rounding_priority = rounding_priority_option.as_string().utf8_string();
+    auto rounding_priority = rounding_priority_option.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16();
 
     // 11. Let trailingZeroDisplay be ? GetOption(options, "trailingZeroDisplay", STRING, « "auto", "stripIfInteger" », "auto").
     auto trailing_zero_display = TRY(get_option(vm, options, vm.names.trailingZeroDisplay, OptionType::String, { "auto"sv, "stripIfInteger"sv }, "auto"sv));
@@ -217,10 +217,10 @@ ThrowCompletionOr<void> set_number_format_digit_options(VM& vm, NumberFormatBase
     intl_object.set_rounding_increment(*rounding_increment);
 
     // 15. Set intlObj.[[RoundingMode]] to roundingMode.
-    intl_object.set_rounding_mode(rounding_mode.as_string().utf8_string());
+    intl_object.set_rounding_mode(rounding_mode.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16());
 
     // 16. Set intlObj.[[TrailingZeroDisplay]] to trailingZeroDisplay.
-    intl_object.set_trailing_zero_display(trailing_zero_display.as_string().utf8_string());
+    intl_object.set_trailing_zero_display(trailing_zero_display.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16());
 
     // 17. If mnsd is undefined and mxsd is undefined, let hasSd be false. Otherwise, let hasSd be true.
     bool has_significant_digits = !min_significant_digits.is_undefined() || !max_significant_digits.is_undefined();
@@ -379,7 +379,7 @@ ThrowCompletionOr<void> set_number_format_unit_options(VM& vm, NumberFormat& int
     auto style = TRY(get_option(vm, options, vm.names.style, OptionType::String, { "decimal"sv, "percent"sv, "currency"sv, "unit"sv }, "decimal"sv));
 
     // 2. Set intlObj.[[Style]] to style.
-    intl_object.set_style(style.as_string().utf8_string());
+    intl_object.set_style(style.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16());
 
     // 3. Let currency be ? GetOption(options, "currency", STRING, EMPTY, undefined).
     auto currency = TRY(get_option(vm, options, vm.names.currency, OptionType::String, {}, Empty {}));
@@ -392,7 +392,7 @@ ThrowCompletionOr<void> set_number_format_unit_options(VM& vm, NumberFormat& int
     }
     // 5. Else,
     //     a. If IsWellFormedCurrencyCode(currency) is false, throw a RangeError exception.
-    else if (!is_well_formed_currency_code(currency.as_string().utf8_string())) {
+    else if (!is_well_formed_currency_code(currency.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16())) {
         return vm.throw_completion<RangeError>(ErrorType::OptionIsNotValidValue, currency, "currency"sv);
     }
 
@@ -413,7 +413,7 @@ ThrowCompletionOr<void> set_number_format_unit_options(VM& vm, NumberFormat& int
     }
     // 10. Else,
     //     a. If IsWellFormedUnitIdentifier(unit) is false, throw a RangeError exception.
-    else if (!is_well_formed_unit_identifier(unit.as_string().utf8_string())) {
+    else if (!is_well_formed_unit_identifier(unit.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16())) {
         return vm.throw_completion<RangeError>(ErrorType::OptionIsNotValidValue, unit, "unit"sv);
     }
 
@@ -423,22 +423,22 @@ ThrowCompletionOr<void> set_number_format_unit_options(VM& vm, NumberFormat& int
     // 12. If style is "currency", then
     if (intl_object.style() == Unicode::NumberFormatStyle::Currency) {
         // a. Set intlObj.[[Currency]] to the ASCII-uppercase of currency.
-        intl_object.set_currency(MUST(currency.as_string().utf8_string().to_uppercase()));
+        intl_object.set_currency(MUST(currency.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16().to_uppercase()));
 
         // c. Set intlObj.[[CurrencyDisplay]] to currencyDisplay.
-        intl_object.set_currency_display(currency_display.as_string().utf8_string());
+        intl_object.set_currency_display(currency_display.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16());
 
         // d. Set intlObj.[[CurrencySign]] to currencySign.
-        intl_object.set_currency_sign(currency_sign.as_string().utf8_string());
+        intl_object.set_currency_sign(currency_sign.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16());
     }
 
     // 13. If style is "unit", then
     if (intl_object.style() == Unicode::NumberFormatStyle::Unit) {
         // a. Set intlObj.[[Unit]] to unit.
-        intl_object.set_unit(unit.as_string().utf8_string());
+        intl_object.set_unit(unit.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16());
 
         // b. Set intlObj.[[UnitDisplay]] to unitDisplay.
-        intl_object.set_unit_display(unit_display.as_string().utf8_string());
+        intl_object.set_unit_display(unit_display.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16());
     }
 
     // 14. Return UNUSED.
diff --git a/Libraries/LibJS/Runtime/Intl/PluralRulesConstructor.cpp b/Libraries/LibJS/Runtime/Intl/PluralRulesConstructor.cpp
index e9f36caff8..7b5f9bf2c6 100644
--- a/Libraries/LibJS/Runtime/Intl/PluralRulesConstructor.cpp
+++ b/Libraries/LibJS/Runtime/Intl/PluralRulesConstructor.cpp
@@ -67,13 +67,13 @@ ThrowCompletionOr<GC::Ref<Object>> PluralRulesConstructor::construct(FunctionObj
     auto type = TRY(get_option(vm, *options, vm.names.type, OptionType::String, AK::Array { "cardinal"sv, "ordinal"sv }, "cardinal"sv));
 
     // 8. Set pluralRules.[[Type]] to t.
-    plural_rules->set_type(type.as_string().utf8_string());
+    plural_rules->set_type(type.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16());
 
     // 9. Let notation be ? GetOption(options, "notation", string, « "standard", "scientific", "engineering", "compact" », "standard").
     auto notation = TRY(get_option(vm, *options, vm.names.notation, OptionType::String, { "standard"sv, "scientific"sv, "engineering"sv, "compact"sv }, "standard"sv));
 
     // 10. Set pluralRules.[[Notation]] to notation.
-    plural_rules->set_notation(notation.as_string().utf8_string());
+    plural_rules->set_notation(notation.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16());
 
     // 11. Let compactDisplay be ? GetOption(options, "compactDisplay", string, « "short", "long" », "short").
     auto compact_display = TRY(get_option(vm, *options, vm.names.compactDisplay, OptionType::String, { "short"sv, "long"sv }, "short"sv));
@@ -81,7 +81,7 @@ ThrowCompletionOr<GC::Ref<Object>> PluralRulesConstructor::construct(FunctionObj
     // 12. If notation is "compact", then
     if (plural_rules->notation() == Unicode::Notation::Compact) {
         // a. Set pluralRules.[[CompactDisplay]] to compactDisplay.
-        plural_rules->set_compact_display(compact_display.as_string().utf8_string());
+        plural_rules->set_compact_display(compact_display.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16());
     }
 
     // 13. Perform ? SetNumberFormatDigitOptions(pluralRules, options, 0, 3, notation).
diff --git a/Libraries/LibJS/Runtime/Intl/RelativeTimeFormatConstructor.cpp b/Libraries/LibJS/Runtime/Intl/RelativeTimeFormatConstructor.cpp
index 724246badc..d4607b5a1b 100644
--- a/Libraries/LibJS/Runtime/Intl/RelativeTimeFormatConstructor.cpp
+++ b/Libraries/LibJS/Runtime/Intl/RelativeTimeFormatConstructor.cpp
@@ -75,13 +75,13 @@ ThrowCompletionOr<GC::Ref<Object>> RelativeTimeFormatConstructor::construct(Func
     auto style = TRY(get_option(vm, *options, vm.names.style, OptionType::String, { "long"sv, "short"sv, "narrow"sv }, "long"sv));
 
     // 11. Set relativeTimeFormat.[[Style]] to style.
-    relative_time_format->set_style(style.as_string().utf8_string());
+    relative_time_format->set_style(style.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16());
 
     // 12. Let numeric be ? GetOption(options, "numeric", STRING, « "always", "auto" », "always").
     auto numeric = TRY(get_option(vm, *options, vm.names.numeric, OptionType::String, { "always"sv, "auto"sv }, "always"sv));
 
     // 13. Set relativeTimeFormat.[[Numeric]] to numeric.
-    relative_time_format->set_numeric(numeric.as_string().utf8_string());
+    relative_time_format->set_numeric(numeric.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16());
 
     // 14. Let nfOptions be OrdinaryObjectCreate(null).
     // 15. Perform ! CreateDataPropertyOrThrow(nfOptions, "numberingSystem", relativeTimeFormat.[[NumberingSystem]]).
diff --git a/Libraries/LibJS/Runtime/Intl/RelativeTimeFormatPrototype.cpp b/Libraries/LibJS/Runtime/Intl/RelativeTimeFormatPrototype.cpp
index 72331ed64b..a7ffd8b05c 100644
--- a/Libraries/LibJS/Runtime/Intl/RelativeTimeFormatPrototype.cpp
+++ b/Libraries/LibJS/Runtime/Intl/RelativeTimeFormatPrototype.cpp
@@ -71,10 +71,10 @@ JS_DEFINE_NATIVE_FUNCTION(RelativeTimeFormatPrototype::format)
     auto value = TRY(vm.argument(0).to_number(vm));
 
     // 4. Let unit be ? ToString(unit).
-    auto unit = TRY(vm.argument(1).to_string(vm));
+    auto unit = TRY(vm.argument(1).to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16();
 
     // 5. Return ? FormatRelativeTime(relativeTimeFormat, value, unit).
-    auto formatted = TRY(format_relative_time(vm, relative_time_format, value.as_double(), unit.bytes_as_string_view()));
+    auto formatted = TRY(format_relative_time(vm, relative_time_format, value.as_double(), unit));
     return PrimitiveString::create(vm, move(formatted));
 }
 
@@ -89,10 +89,10 @@ JS_DEFINE_NATIVE_FUNCTION(RelativeTimeFormatPrototype::format_to_parts)
     auto value = TRY(vm.argument(0).to_number(vm));
 
     // 4. Let unit be ? ToString(unit).
-    auto unit = TRY(vm.argument(1).to_string(vm));
+    auto unit = TRY(vm.argument(1).to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16();
 
     // 5. Return ? FormatRelativeTimeToParts(relativeTimeFormat, value, unit).
-    return TRY(format_relative_time_to_parts(vm, relative_time_format, value.as_double(), unit.bytes_as_string_view()));
+    return TRY(format_relative_time_to_parts(vm, relative_time_format, value.as_double(), unit));
 }
 
 }
diff --git a/Libraries/LibJS/Runtime/Intl/SegmenterConstructor.cpp b/Libraries/LibJS/Runtime/Intl/SegmenterConstructor.cpp
index 288838655c..7768cc020f 100644
--- a/Libraries/LibJS/Runtime/Intl/SegmenterConstructor.cpp
+++ b/Libraries/LibJS/Runtime/Intl/SegmenterConstructor.cpp
@@ -67,7 +67,7 @@ ThrowCompletionOr<GC::Ref<Object>> SegmenterConstructor::construct(FunctionObjec
     auto granularity = TRY(get_option(vm, *options, vm.names.granularity, OptionType::String, { "grapheme"sv, "word"sv, "sentence"sv }, "grapheme"sv));
 
     // 9. Set segmenter.[[SegmenterGranularity]] to granularity.
-    segmenter->set_segmenter_granularity(granularity.as_string().utf8_string());
+    segmenter->set_segmenter_granularity(granularity.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16());
 
     auto locale_segmenter = Unicode::Segmenter::create(segmenter->locale(), segmenter->segmenter_granularity());
     segmenter->set_segmenter(move(locale_segmenter));
diff --git a/Libraries/LibJS/Runtime/JSONObject.cpp b/Libraries/LibJS/Runtime/JSONObject.cpp
index 2b302e719c..a65eba362f 100644
--- a/Libraries/LibJS/Runtime/JSONObject.cpp
+++ b/Libraries/LibJS/Runtime/JSONObject.cpp
@@ -445,7 +445,7 @@ JS_DEFINE_NATIVE_FUNCTION(JSONObject::parse)
     auto reviver = vm.argument(1);
 
     // 1. Let jsonString be ? ToString(text).
-    auto json_string = TRY(text.to_string(vm));
+    auto json_string = TRY(text.to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16();
 
     // 2. Let parseResult be ? ParseJSON(jsonString).
     // 3. Let unfiltered be parseResult.[[Value]].
@@ -996,7 +996,7 @@ JS_DEFINE_NATIVE_FUNCTION(JSONObject::raw_json)
     auto& realm = *vm.current_realm();
 
     // 1. Let jsonString be ? ToString(text).
-    auto json_string = TRY(vm.argument(0).to_string(vm));
+    auto json_string = TRY(vm.argument(0).to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16();
 
     // 2. Throw a SyntaxError exception if jsonString is the empty String, or if either the first or last code unit of
     //    jsonString is any of 0x0009 (CHARACTER TABULATION), 0x000A (LINE FEED), 0x000D (CARRIAGE RETURN), or
diff --git a/Libraries/LibJS/Runtime/NumberPrototype.cpp b/Libraries/LibJS/Runtime/NumberPrototype.cpp
index d085f3bcbb..355004852b 100644
--- a/Libraries/LibJS/Runtime/NumberPrototype.cpp
+++ b/Libraries/LibJS/Runtime/NumberPrototype.cpp
@@ -276,7 +276,7 @@ JS_DEFINE_NATIVE_FUNCTION(NumberPrototype::to_exponential)
 
     // 4. If x is not finite, return Number::toString(x).
     if (!number_value.is_finite_number())
-        return PrimitiveString::create(vm, MUST(number_value.to_string(vm)));
+        return PrimitiveString::create(vm, MUST(number_value.to_utf16_string(vm)));
 
     // 5. If f < 0 or f > 100, throw a RangeError exception.
     if (fraction_digits < 0 || fraction_digits > 100)
@@ -408,7 +408,7 @@ JS_DEFINE_NATIVE_FUNCTION(NumberPrototype::to_fixed)
 
     // 6. If x is not finite, return Number::toString(x).
     if (!number_value.is_finite_number())
-        return PrimitiveString::create(vm, TRY(number_value.to_string(vm)));
+        return PrimitiveString::create(vm, TRY(number_value.to_utf16_string(vm)));
 
     // 7. Set x to ℝ(x).
     auto number = number_value.as_double();
@@ -424,7 +424,7 @@ JS_DEFINE_NATIVE_FUNCTION(NumberPrototype::to_fixed)
     // 10. If x ≥ 10^21, then
     //     a. Let m be ! ToString(𝔽(x)).
     if (number >= 1e+21)
-        return PrimitiveString::create(vm, MUST(number_value.to_string(vm)));
+        return PrimitiveString::create(vm, MUST(number_value.to_utf16_string(vm)));
 
     // 11. Else,
     //     a. Let n be an integer for which n / (10^f) - x is as close to zero as possible. If there are two such n, pick the larger n.
@@ -489,14 +489,14 @@ JS_DEFINE_NATIVE_FUNCTION(NumberPrototype::to_precision)
 
     // 2. If precision is undefined, return ! ToString(x).
     if (precision_value.is_undefined())
-        return PrimitiveString::create(vm, MUST(number_value.to_string(vm)));
+        return PrimitiveString::create(vm, MUST(number_value.to_utf16_string(vm)));
 
     // 3. Let p be ? ToIntegerOrInfinity(precision).
     auto precision = TRY(precision_value.to_integer_or_infinity(vm));
 
     // 4. If x is not finite, return Number::toString(x).
     if (!number_value.is_finite_number())
-        return PrimitiveString::create(vm, MUST(number_value.to_string(vm)));
+        return PrimitiveString::create(vm, MUST(number_value.to_utf16_string(vm)));
 
     // 5. If p < 1 or p > 100, throw a RangeError exception.
     if ((precision < 1) || (precision > 100))
@@ -629,7 +629,7 @@ JS_DEFINE_NATIVE_FUNCTION(NumberPrototype::to_string)
 
     // 5. If radixMV = 10, return ! ToString(x).
     if (radix_mv == 10)
-        return PrimitiveString::create(vm, MUST(number_value.to_string(vm)));
+        return PrimitiveString::create(vm, MUST(number_value.to_utf16_string(vm)));
 
     // 6. Return the String representation of this Number value using the radix specified by radixMV. Letters a-z are used for digits with values 10 through 35. The precise algorithm is implementation-defined, however the algorithm should be a generalization of that specified in 6.1.6.1.20.
     if (number_value.is_positive_infinity())
diff --git a/Libraries/LibJS/Runtime/ObjectPrototype.cpp b/Libraries/LibJS/Runtime/ObjectPrototype.cpp
index fadc42890e..ac6dfa14f9 100644
--- a/Libraries/LibJS/Runtime/ObjectPrototype.cpp
+++ b/Libraries/LibJS/Runtime/ObjectPrototype.cpp
@@ -193,7 +193,7 @@ JS_DEFINE_NATIVE_FUNCTION(ObjectPrototype::to_string)
     if (!to_string_tag.is_string())
         tag = builtin_tag;
     else {
-        custom_tag = to_string_tag.as_string().utf8_string();
+        custom_tag = to_string_tag.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16();
         tag = custom_tag;
     }
 
diff --git a/Libraries/LibJS/Runtime/PrimitiveString.cpp b/Libraries/LibJS/Runtime/PrimitiveString.cpp
index 28f5e9d14f..3e5ad361e9 100644
--- a/Libraries/LibJS/Runtime/PrimitiveString.cpp
+++ b/Libraries/LibJS/Runtime/PrimitiveString.cpp
@@ -211,11 +211,6 @@ bool PrimitiveString::is_empty() const
     VERIFY_NOT_REACHED();
 }
 
-String PrimitiveString::utf8_string() const
-{
-    return utf16_string_view().to_utf8_but_should_be_ported_to_utf16();
-}
-
 Utf16String PrimitiveString::utf16_string() const
 {
     resolve_if_needed();
diff --git a/Libraries/LibJS/Runtime/PrimitiveString.h b/Libraries/LibJS/Runtime/PrimitiveString.h
index c04b94b123..41884677fd 100644
--- a/Libraries/LibJS/Runtime/PrimitiveString.h
+++ b/Libraries/LibJS/Runtime/PrimitiveString.h
@@ -47,8 +47,6 @@ public:
 
     bool is_empty() const;
 
-    [[nodiscard]] String utf8_string() const;
-
     [[nodiscard]] Utf16String utf16_string() const;
     [[nodiscard]] Utf16View utf16_string_view() const;
     bool has_utf16_string() const { return m_utf16_string.has_value(); }
diff --git a/Libraries/LibJS/Runtime/RegExpConstructor.cpp b/Libraries/LibJS/Runtime/RegExpConstructor.cpp
index 00337f8f55..a1510cf829 100644
--- a/Libraries/LibJS/Runtime/RegExpConstructor.cpp
+++ b/Libraries/LibJS/Runtime/RegExpConstructor.cpp
@@ -257,10 +257,10 @@ JS_DEFINE_NATIVE_FUNCTION(RegExpConstructor::escape)
         return vm.throw_completion<TypeError>(ErrorType::NotAString, string);
 
     // 2. Let escaped be the empty String.
+    auto code_point_list = string.as_string().utf16_string_view();
     Utf16StringBuilder escaped(string.as_string().utf16_string_view().length_in_code_units());
 
     // 3. Let cpList be StringToCodePoints(S).
-    auto code_point_list = string.as_string().utf16_string_view();
 
     // 4. For each code point c of cpList, do
     for (auto code_point : code_point_list) {
diff --git a/Libraries/LibJS/Runtime/RegExpPrototype.cpp b/Libraries/LibJS/Runtime/RegExpPrototype.cpp
index 64c2630c25..ebfffa2f14 100644
--- a/Libraries/LibJS/Runtime/RegExpPrototype.cpp
+++ b/Libraries/LibJS/Runtime/RegExpPrototype.cpp
@@ -556,7 +556,7 @@ JS_DEFINE_NATIVE_FUNCTION(RegExpPrototype::symbol_match)
     // 4. Let flags be ? ToString(? Get(rx, "flags")).
     static auto& cache = *new Bytecode::StaticPropertyLookupCache;
     auto flags_value = TRY(regexp_object->get(vm.names.flags, cache));
-    auto flags = TRY(flags_value.to_string(vm));
+    auto flags = TRY(flags_value.to_utf16_string(vm));
 
     // 5. If flags does not contain "g", then
     if (!flags.contains('g')) {
@@ -600,7 +600,7 @@ JS_DEFINE_NATIVE_FUNCTION(RegExpPrototype::symbol_match)
 
         // 1. Let matchStr be ? ToString(? Get(result, "0")).
         auto match_value = TRY(result.get(0));
-        auto match_str = TRY(match_value.to_string(vm));
+        auto match_str = TRY(match_value.to_utf16_string(vm));
 
         // 2. Perform ! CreateDataPropertyOrThrow(A, ! ToString(𝔽(n)), matchStr).
         array->indexed_put(n, PrimitiveString::create(vm, match_str));
@@ -634,7 +634,7 @@ JS_DEFINE_NATIVE_FUNCTION(RegExpPrototype::symbol_match_all)
     // 5. Let flags be ? ToString(? Get(R, "flags")).
     static auto& cache = *new Bytecode::StaticPropertyLookupCache;
     auto flags_value = TRY(regexp_object->get(vm.names.flags, cache));
-    auto flags = TRY(flags_value.to_string(vm));
+    auto flags = TRY(flags_value.to_utf16_string(vm));
 
     // Steps 9-12 are performed early so that flags can be moved.
 
@@ -908,14 +908,14 @@ ThrowCompletionOr<Value> RegExpPrototype::symbol_replace_impl(VM& vm, Object& re
     // 6. If functionalReplace is false, then
     if (!replace_value.is_function()) {
         // a. Set replaceValue to ? ToString(replaceValue).
-        auto replace_string = TRY(replace_value.to_string(vm));
+        auto replace_string = TRY(replace_value.to_utf16_string(vm));
         replace_value = PrimitiveString::create(vm, move(replace_string));
     }
 
     // 7. Let flags be ? ToString(? Get(rx, "flags")).
     static auto& cache = *new Bytecode::StaticPropertyLookupCache;
     auto flags_value = TRY(regexp_object.get(vm.names.flags, cache));
-    auto flags = TRY(flags_value.to_string(vm));
+    auto flags = TRY(flags_value.to_utf16_string(vm));
 
     // 8. If flags contains "g", let global be true. Otherwise, let global be false.
     bool global = flags.contains('g');
@@ -953,7 +953,7 @@ ThrowCompletionOr<Value> RegExpPrototype::symbol_replace_impl(VM& vm, Object& re
 
         // 1. Let matchStr be ? ToString(? Get(result, "0")).
         auto match_value = TRY(result.get(vm, 0));
-        auto match_str = TRY(match_value.to_string(vm));
+        auto match_str = TRY(match_value.to_utf16_string(vm));
 
         // 2. If matchStr is the empty String, then
         if (match_str.is_empty()) {
@@ -1007,7 +1007,7 @@ ThrowCompletionOr<Value> RegExpPrototype::symbol_replace_impl(VM& vm, Object& re
             // ii. If capN is not undefined, then
             if (!capture.is_undefined()) {
                 // 1. Set capN to ? ToString(capN).
-                capture = PrimitiveString::create(vm, TRY(capture.to_string(vm)));
+                capture = PrimitiveString::create(vm, TRY(capture.to_utf16_string(vm)));
             }
 
             // iii. Append capN as the last element of captures.
@@ -1316,7 +1316,7 @@ ThrowCompletionOr<Value> RegExpPrototype::symbol_split_impl(VM& vm, Object& rege
     // 5. Let flags be ? ToString(? Get(rx, "flags")).
     static auto& cache = *new Bytecode::StaticPropertyLookupCache;
     auto flags_value = TRY(regexp_object.get(vm.names.flags, cache));
-    auto flags = TRY(flags_value.to_string(vm));
+    auto flags = TRY(flags_value.to_utf16_string(vm));
 
     // 6. If flags contains "u" or flags contains "v", let unicodeMatching be true.
     // 7. Else, let unicodeMatching be false.
@@ -1324,7 +1324,7 @@ ThrowCompletionOr<Value> RegExpPrototype::symbol_split_impl(VM& vm, Object& rege
 
     // 8. If flags contains "y", let newFlags be flags.
     // 9. Else, let newFlags be the string-concatenation of flags and "y".
-    auto new_flags = flags.bytes_as_string_view().find('y').has_value() ? move(flags) : MUST(String::formatted("{}y", flags));
+    auto new_flags = flags.contains('y') ? move(flags) : Utf16String::formatted("{}y", flags);
 
     // 10. Let splitter be ? Construct(C, « rx, newFlags »).
     auto splitter = TRY(construct(vm, *constructor, &regexp_object, PrimitiveString::create(vm, move(new_flags))));
@@ -1544,12 +1544,12 @@ JS_DEFINE_NATIVE_FUNCTION(RegExpPrototype::to_string)
     // 3. Let pattern be ? ToString(? Get(R, "source")).
     static auto& cache = *new Bytecode::StaticPropertyLookupCache;
     auto source_attr = TRY(regexp_object->get(vm.names.source, cache));
-    auto pattern = TRY(source_attr.to_string(vm));
+    auto pattern = TRY(source_attr.to_utf16_string(vm));
 
     // 4. Let flags be ? ToString(? Get(R, "flags")).
     static auto& cache2 = *new Bytecode::StaticPropertyLookupCache;
     auto flags_attr = TRY(regexp_object->get(vm.names.flags, cache2));
-    auto flags = TRY(flags_attr.to_string(vm));
+    auto flags = TRY(flags_attr.to_utf16_string(vm));
 
     // 5. Let result be the string-concatenation of "/", pattern, "/", and flags.
     // 6. Return result.
diff --git a/Libraries/LibJS/Runtime/StringPrototype.cpp b/Libraries/LibJS/Runtime/StringPrototype.cpp
index dca8874a02..23447708a8 100644
--- a/Libraries/LibJS/Runtime/StringPrototype.cpp
+++ b/Libraries/LibJS/Runtime/StringPrototype.cpp
@@ -40,7 +40,7 @@ GC_DEFINE_ALLOCATOR(StringPrototype);
 static ThrowCompletionOr<String> utf8_string_from(VM& vm)
 {
     auto this_value = TRY(require_object_coercible(vm, vm.this_value()));
-    return TRY(this_value.to_string(vm));
+    return TRY(this_value.to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16();
 }
 
 static ThrowCompletionOr<GC::Ref<PrimitiveString>> primitive_string_from(VM& vm)
@@ -673,7 +673,7 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::match_all)
             auto flags_object = TRY(require_object_coercible(vm, flags));
 
             // iii. If ? ToString(flags) does not contain "g", throw a TypeError exception.
-            auto flags_string = TRY(flags_object.to_string(vm));
+            auto flags_string = TRY(flags_object.to_utf16_string(vm));
             if (!flags_string.contains('g'))
                 return vm.throw_completion<TypeError>(ErrorType::StringNonGlobalRegExp);
         }
@@ -714,7 +714,7 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::normalize)
     }
     // 4. Else, let f be ? ToString(form).
     else {
-        form = TRY(form_value.to_string(vm));
+        form = TRY(form_value.to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16();
     }
 
     // 5. If f is not one of "NFC", "NFD", "NFKC", or "NFKD", throw a RangeError exception.
@@ -953,7 +953,7 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::replace_all)
             auto flags_object = TRY(require_object_coercible(vm, flags));
 
             // iii. If ? ToString(flags) does not contain "g", throw a TypeError exception.
-            if (!TRY(flags_object.to_string(vm)).contains('g'))
+            if (!TRY(flags_object.to_utf16_string(vm)).contains('g'))
                 return vm.throw_completion<TypeError>(ErrorType::StringNonGlobalRegExp);
         }
 
@@ -1479,23 +1479,23 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::to_well_formed)
 }
 
 // 22.1.3.32.1 TrimString ( string, where ), https://tc39.es/ecma262/#sec-trimstring
-ThrowCompletionOr<String> trim_string(VM& vm, Value input_value, TrimMode where)
+ThrowCompletionOr<Utf16String> trim_string(VM& vm, Value input_value, TrimMode where)
 {
     // 1. Let str be ? RequireObjectCoercible(string).
     auto input_string = TRY(require_object_coercible(vm, input_value));
 
     // 2. Let S be ? ToString(str).
-    auto string = TRY(input_string.to_string(vm));
+    auto string = TRY(input_string.to_utf16_string(vm));
 
     // 3. If where is start, let T be the String value that is a copy of S with leading white space removed.
     // 4. Else if where is end, let T be the String value that is a copy of S with trailing white space removed.
     // 5. Else,
     // a. Assert: where is start+end.
     // b. Let T be the String value that is a copy of S with both leading and trailing white space removed.
-    auto trimmed_string = Utf8View(string).trim(whitespace_characters, where).as_string();
+    auto trimmed_string = string.trim(whitespace_characters, where);
 
     // 6. Return T.
-    return MUST(String::from_utf8(trimmed_string));
+    return trimmed_string;
 }
 
 // 22.1.3.32 String.prototype.trim ( ), https://tc39.es/ecma262/#sec-string.prototype.trim
@@ -1537,7 +1537,7 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::symbol_iterator)
     auto this_object = TRY(require_object_coercible(vm, vm.this_value()));
 
     // 2. Let s be ? ToString(O).
-    auto string = TRY(this_object.to_string(vm));
+    auto string = TRY(this_object.to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16();
 
     // 3. Let closure be a new Abstract Closure with no parameters that captures s and performs the following steps when called:
     //     ...
@@ -1605,7 +1605,7 @@ static ThrowCompletionOr<Value> create_html(VM& vm, Value string, StringView tag
         auto value_string = TRY(value.to_utf16_string(vm));
 
         // b. Let escapedV be the String value that is the same as V except that each occurrence of the code unit 0x0022 (QUOTATION MARK) in V has been replaced with the six code unit sequence "&quot;".
-        auto escaped_value_string = value_string.replace("\""sv, "&quot;"sv, ReplaceMode::All);
+        auto escaped_value_string = value_string.replace(u'"', "&quot;"sv, ReplaceMode::All);
 
         // c. Set p1 to the string-concatenation of:
         // - p1
diff --git a/Libraries/LibJS/Runtime/StringPrototype.h b/Libraries/LibJS/Runtime/StringPrototype.h
index acc0e32051..2998f32d7e 100644
--- a/Libraries/LibJS/Runtime/StringPrototype.h
+++ b/Libraries/LibJS/Runtime/StringPrototype.h
@@ -6,7 +6,7 @@
 
 #pragma once
 
-#include <AK/Utf8View.h>
+#include <AK/Utf16View.h>
 #include <LibJS/Runtime/StringObject.h>
 
 namespace JS {
@@ -20,8 +20,35 @@ struct CodePoint {
 Optional<size_t> string_index_of(Utf16View const& string, Utf16View const& search_value, size_t from_index);
 Optional<size_t> string_last_index_of(Utf16View const& string, Utf16View const& search_value, size_t from_index);
 CodePoint code_point_at(Utf16View const& string, size_t position);
-static constexpr Utf8View whitespace_characters = Utf8View("\x09\x0A\x0B\x0C\x0D\x20\xC2\xA0\xE1\x9A\x80\xE2\x80\x80\xE2\x80\x81\xE2\x80\x82\xE2\x80\x83\xE2\x80\x84\xE2\x80\x85\xE2\x80\x86\xE2\x80\x87\xE2\x80\x88\xE2\x80\x89\xE2\x80\x8A\xE2\x80\xAF\xE2\x81\x9F\xE3\x80\x80\xE2\x80\xA8\xE2\x80\xA9\xEF\xBB\xBF"sv);
-ThrowCompletionOr<String> trim_string(VM&, Value string, TrimMode where);
+static constexpr char16_t whitespace_character_code_units[] = {
+    u'\u0009',
+    u'\u000A',
+    u'\u000B',
+    u'\u000C',
+    u'\u000D',
+    u'\u0020',
+    u'\u00A0',
+    u'\u1680',
+    u'\u2000',
+    u'\u2001',
+    u'\u2002',
+    u'\u2003',
+    u'\u2004',
+    u'\u2005',
+    u'\u2006',
+    u'\u2007',
+    u'\u2008',
+    u'\u2009',
+    u'\u200A',
+    u'\u2028',
+    u'\u2029',
+    u'\u202F',
+    u'\u205F',
+    u'\u3000',
+    u'\uFEFF',
+};
+static constexpr Utf16View whitespace_characters { whitespace_character_code_units, 25 };
+ThrowCompletionOr<Utf16String> trim_string(VM&, Value string, TrimMode where);
 
 class StringPrototype final : public StringObject {
     JS_OBJECT(StringPrototype, StringObject);
diff --git a/Libraries/LibJS/Runtime/SuppressedErrorConstructor.cpp b/Libraries/LibJS/Runtime/SuppressedErrorConstructor.cpp
index bf97216374..5fef84a2dc 100644
--- a/Libraries/LibJS/Runtime/SuppressedErrorConstructor.cpp
+++ b/Libraries/LibJS/Runtime/SuppressedErrorConstructor.cpp
@@ -54,7 +54,7 @@ ThrowCompletionOr<GC::Ref<Object>> SuppressedErrorConstructor::construct(Functio
     // 3. If message is not undefined, then
     if (!message.is_undefined()) {
         // a. Let msg be ? ToString(message).
-        auto msg = TRY(message.to_string(vm));
+        auto msg = TRY(message.to_utf16_string(vm));
 
         // b. Perform CreateNonEnumerableDataPropertyOrThrow(O, "message", msg).
         suppressed_error->create_non_enumerable_data_property_or_throw(vm.names.message, PrimitiveString::create(vm, move(msg)));
diff --git a/Libraries/LibJS/Runtime/Temporal/AbstractOperations.cpp b/Libraries/LibJS/Runtime/Temporal/AbstractOperations.cpp
index e3712ac9d4..278f3dd509 100644
--- a/Libraries/LibJS/Runtime/Temporal/AbstractOperations.cpp
+++ b/Libraries/LibJS/Runtime/Temporal/AbstractOperations.cpp
@@ -90,7 +90,7 @@ ThrowCompletionOr<Overflow> get_temporal_overflow_option(VM& vm, Object const& o
     auto string_value = TRY(get_option(vm, options, vm.names.overflow, OptionType::String, { "constrain"sv, "reject"sv }, "constrain"sv));
 
     // 2. If stringValue is "constrain", return CONSTRAIN.
-    if (string_value.as_string().utf8_string() == "constrain"sv)
+    if (string_value.as_string().utf16_string_view() == "constrain"sv)
         return Overflow::Constrain;
 
     // 3. Return REJECT.
@@ -102,7 +102,7 @@ ThrowCompletionOr<Disambiguation> get_temporal_disambiguation_option(VM& vm, Obj
 {
     // 1. Let stringValue be ? GetOption(options, "disambiguation", STRING, « "compatible", "earlier", "later", "reject" », "compatible").
     auto string_value = TRY(get_option(vm, options, vm.names.disambiguation, OptionType::String, { "compatible"sv, "earlier"sv, "later"sv, "reject"sv }, "compatible"sv));
-    auto string_view = string_value.as_string().utf8_string();
+    auto string_view = string_value.as_string().utf16_string_view();
 
     // 2. If stringValue is "compatible", return COMPATIBLE.
     if (string_view == "compatible"sv)
@@ -166,7 +166,7 @@ ThrowCompletionOr<OffsetOption> get_temporal_offset_option(VM& vm, Object const&
 
     // 5. Let stringValue be ? GetOption(options, "offset", STRING, « "prefer", "use", "ignore", "reject" », stringFallback).
     auto string_value = TRY(get_option(vm, options, vm.names.offset, OptionType::String, { "prefer"sv, "use"sv, "ignore"sv, "reject"sv }, string_fallback));
-    auto string_view = string_value.as_string().utf8_string();
+    auto string_view = string_value.as_string().utf16_string_view();
 
     // 6. If stringValue is "prefer", return PREFER.
     if (string_view == "prefer"sv)
@@ -189,7 +189,7 @@ ThrowCompletionOr<ShowCalendar> get_temporal_show_calendar_name_option(VM& vm, O
 {
     // 1. Let stringValue be ? GetOption(options, "calendarName", STRING, « "auto", "always", "never", "critical" », "auto").
     auto string_value = TRY(get_option(vm, options, vm.names.calendarName, OptionType::String, { "auto"sv, "always"sv, "never"sv, "critical"sv }, "auto"sv));
-    auto string_view = string_value.as_string().utf8_string();
+    auto string_view = string_value.as_string().utf16_string_view();
 
     // 2. If stringValue is "always", return ALWAYS.
     if (string_view == "always"sv)
@@ -212,7 +212,7 @@ ThrowCompletionOr<ShowTimeZoneName> get_temporal_show_time_zone_name_option(VM&
 {
     // 1. Let stringValue be ? GetOption(options, "timeZoneName", STRING, « "auto", "never", "critical" », "auto").
     auto string_value = TRY(get_option(vm, options, vm.names.timeZoneName, OptionType::String, { "auto"sv, "never"sv, "critical"sv }, "auto"sv));
-    auto string_view = string_value.as_string().utf8_string();
+    auto string_view = string_value.as_string().utf16_string_view();
 
     // 2. If stringValue is "never", return NEVER.
     if (string_view == "never"sv)
@@ -231,7 +231,7 @@ ThrowCompletionOr<ShowOffset> get_temporal_show_offset_option(VM& vm, Object con
 {
     // 1. Let stringValue be ? GetOption(options, "offset", STRING, « "auto", "never" », "auto").
     auto string_value = TRY(get_option(vm, options, vm.names.offset, OptionType::String, { "auto"sv, "never"sv }, "auto"sv));
-    auto string_view = string_value.as_string().utf8_string();
+    auto string_view = string_value.as_string().utf16_string_view();
 
     // 2. If stringValue is "never", return never.
     if (string_view == "never"sv)
@@ -246,7 +246,7 @@ ThrowCompletionOr<Direction> get_direction_option(VM& vm, Object const& options)
 {
     // 1. Let stringValue be ? GetOption(options, "direction", STRING, « "next", "previous" », REQUIRED).
     auto string_value = TRY(get_option(vm, options, vm.names.direction, OptionType::String, { "next"sv, "previous"sv }, Required {}));
-    auto string_view = string_value.as_string().utf8_string();
+    auto string_view = string_value.as_string().utf16_string_view();
 
     // 2. If stringValue is "next", return NEXT.
     if (string_view == "next"sv)
@@ -300,7 +300,7 @@ ThrowCompletionOr<Precision> get_temporal_fractional_second_digits_option(VM& vm
     // 3. If digitsValue is not a Number, then
     if (!digits_value.is_number()) {
         // a. If ? ToString(digitsValue) is not "auto", throw a RangeError exception.
-        auto digits_value_string = TRY(digits_value.to_string(vm));
+        auto digits_value_string = TRY(digits_value.to_utf16_string(vm));
 
         if (digits_value_string != "auto"sv)
             return vm.throw_completion<RangeError>(ErrorType::OptionIsNotValidValue, digits_value, vm.names.fractionalSecondDigits);
@@ -415,7 +415,7 @@ ThrowCompletionOr<UnitValue> get_temporal_unit_valued_option(VM& vm, Object cons
     if (value.is_undefined())
         return UnitValue { Unset {} };
 
-    auto value_string = value.as_string().utf8_string();
+    auto value_string = value.as_string().utf16_string_view();
 
     // 8. If value is "auto", return AUTO.
     if (value_string == "auto"sv)
@@ -544,7 +544,7 @@ ThrowCompletionOr<RelativeTo> get_temporal_relative_to_option(VM& vm, Object con
             return vm.throw_completion<TypeError>(ErrorType::NotAString, vm.names.relativeTo);
 
         // b. Let result be ? ParseISODateTime(value, « TemporalDateTimeString[+Zoned], TemporalDateTimeString[~Zoned] »).
-        auto result = TRY(parse_iso_date_time(vm, value.as_string().utf8_string(), { { Production::TemporalZonedDateTimeString, Production::TemporalDateTimeString } }));
+        auto result = TRY(parse_iso_date_time(vm, value.as_string().utf16_string_view(), { { Production::TemporalZonedDateTimeString, Production::TemporalDateTimeString } }));
 
         // c. Let offsetString be result.[[TimeZone]].[[OffsetString]].
         offset_string = move(result.time_zone.offset_string);
@@ -560,7 +560,8 @@ ThrowCompletionOr<RelativeTo> get_temporal_relative_to_option(VM& vm, Object con
         // f. Else,
         else {
             // i. Let timeZone be ? ToTemporalTimeZoneIdentifier(annotation).
-            time_zone = TRY(to_temporal_time_zone_identifier(vm, *annotation));
+            auto utf16_annotation = Utf16String::from_utf8(*annotation);
+            time_zone = TRY(to_temporal_time_zone_identifier(vm, utf16_annotation));
 
             // ii. If result.[[TimeZone]].[[Z]] is true, then
             if (result.time_zone.z_designator) {
@@ -579,7 +580,8 @@ ThrowCompletionOr<RelativeTo> get_temporal_relative_to_option(VM& vm, Object con
             // v. If offsetString is not EMPTY, then
             if (offset_string.has_value()) {
                 // 1. Let offsetParseResult be ParseText(StringToCodePoints(offsetString), UTCOffset[+SubMinutePrecision]).
-                auto offset_parse_result = parse_utc_offset(*offset_string, SubMinutePrecision::Yes);
+                auto utf16_offset_string = Utf16String::from_utf8(*offset_string);
+                auto offset_parse_result = parse_utc_offset(utf16_offset_string, SubMinutePrecision::Yes);
 
                 // 2. Assert: offsetParseResult is a Parse Node.
                 VERIFY(offset_parse_result.has_value());
@@ -618,7 +620,7 @@ ThrowCompletionOr<RelativeTo> get_temporal_relative_to_option(VM& vm, Object con
     // 8. If offsetBehaviour is OPTION, then
     if (offset_behavior == OffsetBehavior::Option) {
         // a. Let offsetNs be ! ParseDateTimeUTCOffset(offsetString).
-        offset_nanoseconds = parse_date_time_utc_offset(*offset_string);
+        offset_nanoseconds = parse_date_time_utc_offset(offset_string->bytes_as_string_view());
     }
     // 9. Else,
     else {
@@ -1095,7 +1097,7 @@ Crypto::SignedBigInteger round_number_to_increment_as_if_positive(Crypto::Signed
 }
 
 // 13.35 ParseISODateTime ( isoString, allowedFormats ), https://tc39.es/proposal-temporal/#sec-temporal-parseisodatetime
-ThrowCompletionOr<ParsedISODateTime> parse_iso_date_time(VM& vm, StringView iso_string, ReadonlySpan<Production> allowed_formats)
+ThrowCompletionOr<ParsedISODateTime> parse_iso_date_time(VM& vm, Utf16View iso_string, ReadonlySpan<Production> allowed_formats)
 {
     // 1. Let parseResult be EMPTY.
     Optional<ParseResult> parse_result;
@@ -1133,7 +1135,7 @@ ThrowCompletionOr<ParsedISODateTime> parse_iso_date_time(VM& vm, StringView iso_
                     // i. If calendar is EMPTY, then
                     if (!calendar.has_value()) {
                         // i. Set calendar to CodePointsToString(value).
-                        calendar = String::from_utf8_without_validation(value.bytes());
+                        calendar = value.to_utf8_but_should_be_ported_to_utf16();
 
                         // ii. If annotation contains an AnnotationCriticalFlag Parse Node, set calendarWasCritical to true.
                         if (annotation.critical)
@@ -1234,28 +1236,31 @@ ThrowCompletionOr<ParsedISODateTime> parse_iso_date_time(VM& vm, StringView iso_
     // 19. If fSeconds is not empty, then
     if (!fractional_seconds.is_empty()) {
         // a. Let fSecondsDigits be the substring of CodePointsToString(fSeconds) from 1.
+        auto parse_fractional_digits = [](Utf16View digits, size_t offset) {
+            double value = 0;
+            for (size_t i = 0; i < 3; ++i) {
+                value *= 10;
+                auto index = offset + i;
+                if (index < digits.length_in_code_units())
+                    value += parse_ascii_digit(static_cast<char>(digits.code_unit_at(index)));
+            }
+            return value;
+        };
+
         auto fractional_seconds_digits = fractional_seconds.substring_view(1);
 
         // b. Let fSecondsDigitsExtended be the string-concatenation of fSecondsDigits and "000000000".
-        auto fractional_seconds_extended = MUST(String::formatted("{}000000000", fractional_seconds_digits));
-
         // c. Let millisecond be the substring of fSecondsDigitsExtended from 0 to 3.
-        auto millisecond = fractional_seconds_extended.bytes_as_string_view().substring_view(0, 3);
+        // f. Let millisecondMV be ℝ(StringToNumber(millisecond)).
+        millisecond_value = parse_fractional_digits(fractional_seconds_digits, 0);
 
         // d. Let microsecond be the substring of fSecondsDigitsExtended from 3 to 6.
-        auto microsecond = fractional_seconds_extended.bytes_as_string_view().substring_view(3, 3);
+        // g. Let microsecondMV be ℝ(StringToNumber(microsecond)).
+        microsecond_value = parse_fractional_digits(fractional_seconds_digits, 3);
 
         // e. Let nanosecond be the substring of fSecondsDigitsExtended from 6 to 9.
-        auto nanosecond = fractional_seconds_extended.bytes_as_string_view().substring_view(6, 3);
-
-        // f. Let millisecondMV be ℝ(StringToNumber(millisecond)).
-        millisecond_value = string_to_number(millisecond);
-
-        // g. Let microsecondMV be ℝ(StringToNumber(microsecond)).
-        microsecond_value = string_to_number(microsecond);
-
         // h. Let nanosecondMV be ℝ(StringToNumber(nanosecond)).
-        nanosecond_value = string_to_number(nanosecond);
+        nanosecond_value = parse_fractional_digits(fractional_seconds_digits, 6);
     }
     // 20. Else,
     else {
@@ -1286,7 +1291,7 @@ ThrowCompletionOr<ParsedISODateTime> parse_iso_date_time(VM& vm, StringView iso_
     if (parse_result->time_zone_identifier.has_value()) {
         // a. Let identifier be the source text matched by the TimeZoneIdentifier Parse Node contained within parseResult.
         // b. Set timeZoneResult.[[TimeZoneAnnotation]] to CodePointsToString(identifier).
-        time_zone_result.time_zone_annotation = String::from_utf8_without_validation(parse_result->time_zone_identifier->bytes());
+        time_zone_result.time_zone_annotation = parse_result->time_zone_identifier->to_utf8_but_should_be_ported_to_utf16();
     }
 
     // 26. If parseResult contains a UTCDesignator Parse Node, then
@@ -1298,7 +1303,7 @@ ThrowCompletionOr<ParsedISODateTime> parse_iso_date_time(VM& vm, StringView iso_
     else if (parse_result->date_time_offset.has_value()) {
         // a. Let offset be the source text matched by the UTCOffset[+SubMinutePrecision] Parse Node contained within parseResult.
         // b. Set timeZoneResult.[[OffsetString]] to CodePointsToString(offset).
-        time_zone_result.offset_string = String::from_utf8_without_validation(parse_result->date_time_offset->source_text.bytes());
+        time_zone_result.offset_string = parse_result->date_time_offset->source_text.to_utf8_but_should_be_ported_to_utf16();
     }
 
     // 28. If yearAbsent is true, let yearReturn be EMPTY; else let yearReturn be yearMV.
@@ -1311,7 +1316,7 @@ ThrowCompletionOr<ParsedISODateTime> parse_iso_date_time(VM& vm, StringView iso_
 }
 
 // 13.36 ParseTemporalCalendarString ( string ), https://tc39.es/proposal-temporal/#sec-temporal-parsetemporalcalendarstring
-ThrowCompletionOr<String> parse_temporal_calendar_string(VM& vm, String const& string)
+ThrowCompletionOr<String> parse_temporal_calendar_string(VM& vm, Utf16View string)
 {
     // 1. Let parseResult be Completion(ParseISODateTime(string, « TemporalDateTimeString[+Zoned], TemporalDateTimeString[~Zoned],
     //    TemporalInstantString, TemporalTimeString, TemporalMonthDayString, TemporalYearMonthString »)).
@@ -1341,14 +1346,14 @@ ThrowCompletionOr<String> parse_temporal_calendar_string(VM& vm, String const& s
 
     // 4. If parseResult is a List of errors, throw a RangeError exception.
     if (!annotation_parse_result.has_value())
-        return vm.throw_completion<RangeError>(ErrorType::TemporalInvalidCalendarString, string);
+        return vm.throw_completion<RangeError>(ErrorType::TemporalInvalidCalendarString, string.to_utf8_but_should_be_ported_to_utf16());
 
     // 5. Return string.
-    return string;
+    return string.to_utf8_but_should_be_ported_to_utf16();
 }
 
 // 13.37 ParseTemporalDurationString ( isoString ), https://tc39.es/proposal-temporal/#sec-temporal-parsetemporaldurationstring
-ThrowCompletionOr<GC::Ref<Duration>> parse_temporal_duration_string(VM& vm, StringView iso_string)
+ThrowCompletionOr<GC::Ref<Duration>> parse_temporal_duration_string(VM& vm, Utf16View iso_string)
 {
     // 1. Let duration be ParseText(StringToCodePoints(isoString), TemporalDurationString).
     auto parse_result = parse_iso8601(Production::TemporalDurationString, iso_string);
@@ -1461,7 +1466,7 @@ ThrowCompletionOr<GC::Ref<Duration>> parse_temporal_duration_string(VM& vm, Stri
         auto fractional_hours_digits = fractional_hours.substring_view(1);
 
         // c. Let fHoursScale be the length of fHoursDigits.
-        auto fractional_hours_scale = fractional_hours_digits.length();
+        auto fractional_hours_scale = fractional_hours_digits.length_in_code_units();
 
         // d. Let minutesMV be ? ToIntegerWithTruncation(fHoursDigits) / 10**fHoursScale × 60.
         auto minutes_integer = TRY(to_integer_with_truncation(vm, fractional_hours_digits, ErrorType::TemporalInvalidDurationString, iso_string));
@@ -1484,7 +1489,7 @@ ThrowCompletionOr<GC::Ref<Duration>> parse_temporal_duration_string(VM& vm, Stri
         auto fractional_minutes_digits = fractional_minutes.substring_view(1);
 
         // c. Let fMinutesScale be the length of fMinutesDigits.
-        auto fractional_minutes_scale = fractional_minutes_digits.length();
+        auto fractional_minutes_scale = fractional_minutes_digits.length_in_code_units();
 
         // d. Let secondsMV be ? ToIntegerWithTruncation(fMinutesDigits) / 10**fMinutesScale × 60.
         auto seconds_integer = TRY(to_integer_with_truncation(vm, fractional_minutes_digits, ErrorType::TemporalInvalidDurationString, iso_string));
@@ -1508,7 +1513,7 @@ ThrowCompletionOr<GC::Ref<Duration>> parse_temporal_duration_string(VM& vm, Stri
         auto fractional_seconds_digits = fractional_seconds.substring_view(1);
 
         // b. Let fSecondsScale be the length of fSecondsDigits.
-        auto fractional_seconds_scale = fractional_seconds_digits.length();
+        auto fractional_seconds_scale = fractional_seconds_digits.length_in_code_units();
 
         // c. Let millisecondsMV be ? ToIntegerWithTruncation(fSecondsDigits) / 10**fSecondsScale × 1000.
         auto milliseconds_integer = TRY(to_integer_with_truncation(vm, fractional_seconds_digits, ErrorType::TemporalInvalidDurationString, iso_string));
@@ -1568,7 +1573,7 @@ ThrowCompletionOr<GC::Ref<Duration>> parse_temporal_duration_string(VM& vm, Stri
 }
 
 // 13.38 ParseTemporalTimeZoneString ( timeZoneString ), https://tc39.es/proposal-temporal/#sec-temporal-parsetemporaltimezonestring
-ThrowCompletionOr<ParsedTimeZoneIdentifier> parse_temporal_time_zone_string(VM& vm, StringView time_zone_string)
+ThrowCompletionOr<ParsedTimeZoneIdentifier> parse_temporal_time_zone_string(VM& vm, Utf16View time_zone_string)
 {
     // 1. Let parseResult be ParseText(StringToCodePoints(timeZoneString), TimeZoneIdentifier).
     auto parse_result = parse_iso8601(Production::TimeZoneIdentifier, time_zone_string);
@@ -1620,10 +1625,11 @@ ThrowCompletionOr<String> to_offset_string(VM& vm, Value argument)
         return vm.throw_completion<TypeError>(ErrorType::TemporalInvalidTimeZoneString, offset);
 
     // 3. Perform ? ParseDateTimeUTCOffset(offset).
-    TRY(parse_date_time_utc_offset(vm, offset.as_string().utf8_string()));
+    auto offset_string = offset.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16();
+    TRY(parse_date_time_utc_offset(vm, offset_string.bytes_as_string_view()));
 
     // 4. Return offset.
-    return offset.as_string().utf8_string();
+    return offset_string;
 }
 
 // 13.42 ISODateToFields ( calendar, isoDate, type ), https://tc39.es/proposal-temporal/#sec-temporal-isodatetofields
diff --git a/Libraries/LibJS/Runtime/Temporal/AbstractOperations.h b/Libraries/LibJS/Runtime/Temporal/AbstractOperations.h
index 01a6892783..2fcd42df37 100644
--- a/Libraries/LibJS/Runtime/Temporal/AbstractOperations.h
+++ b/Libraries/LibJS/Runtime/Temporal/AbstractOperations.h
@@ -191,10 +191,10 @@ Crypto::SignedBigInteger apply_unsigned_rounding_mode(Crypto::SignedDivisionResu
 double round_number_to_increment(double, u64 increment, RoundingMode);
 Crypto::SignedBigInteger round_number_to_increment(Crypto::SignedBigInteger const&, Crypto::UnsignedBigInteger const& increment, RoundingMode);
 Crypto::SignedBigInteger round_number_to_increment_as_if_positive(Crypto::SignedBigInteger const&, Crypto::UnsignedBigInteger const& increment, RoundingMode);
-ThrowCompletionOr<ParsedISODateTime> parse_iso_date_time(VM&, StringView iso_string, ReadonlySpan<Production> allowed_formats);
-ThrowCompletionOr<String> parse_temporal_calendar_string(VM&, String const&);
-ThrowCompletionOr<GC::Ref<Duration>> parse_temporal_duration_string(VM&, StringView iso_string);
-ThrowCompletionOr<ParsedTimeZoneIdentifier> parse_temporal_time_zone_string(VM&, StringView time_zone_string);
+ThrowCompletionOr<ParsedISODateTime> parse_iso_date_time(VM&, Utf16View iso_string, ReadonlySpan<Production> allowed_formats);
+ThrowCompletionOr<String> parse_temporal_calendar_string(VM&, Utf16View);
+ThrowCompletionOr<GC::Ref<Duration>> parse_temporal_duration_string(VM&, Utf16View iso_string);
+ThrowCompletionOr<ParsedTimeZoneIdentifier> parse_temporal_time_zone_string(VM&, Utf16View time_zone_string);
 ThrowCompletionOr<String> to_offset_string(VM&, Value argument);
 CalendarFields iso_date_to_fields(String const& calendar, ISODate, DateType);
 ThrowCompletionOr<DifferenceSettings> get_difference_settings(VM&, DurationOperation, Object const& options, UnitGroup, ReadonlySpan<Unit> disallowed_units, Unit fallback_smallest_unit, Unit smallest_largest_default_unit);
@@ -215,10 +215,10 @@ ThrowCompletionOr<double> to_integer_with_truncation(VM& vm, Value argument, Err
 }
 
 // 13.40 ToIntegerWithTruncation ( argument ), https://tc39.es/proposal-temporal/#sec-tointegerwithtruncation
-// AD-HOC: We often need to use this AO when we have a parsed StringView. This overload allows callers to avoid creating
+// AD-HOC: We often need to use this AO when we have a parsed Utf16View. This overload allows callers to avoid creating
 //         a PrimitiveString for the primary definition.
 template<typename... Args>
-ThrowCompletionOr<double> to_integer_with_truncation(VM& vm, StringView argument, ErrorType const& error_type, Args&&... args)
+ThrowCompletionOr<double> to_integer_with_truncation(VM& vm, Utf16View argument, ErrorType const& error_type, Args&&... args)
 {
     // 1. Let number be ? ToNumber(argument).
     auto number = string_to_number(argument);
diff --git a/Libraries/LibJS/Runtime/Temporal/Calendar.cpp b/Libraries/LibJS/Runtime/Temporal/Calendar.cpp
index d0d7e00cd3..cbd58b852c 100644
--- a/Libraries/LibJS/Runtime/Temporal/Calendar.cpp
+++ b/Libraries/LibJS/Runtime/Temporal/Calendar.cpp
@@ -284,6 +284,12 @@ ThrowCompletionOr<String> canonicalize_calendar(VM& vm, StringView id)
     return vm.throw_completion<RangeError>(ErrorType::TemporalInvalidCalendarIdentifier, id);
 }
 
+ThrowCompletionOr<String> canonicalize_calendar(VM& vm, Utf16View id)
+{
+    auto utf8_id = id.to_utf8_but_should_be_ported_to_utf16();
+    return canonicalize_calendar(vm, utf8_id.bytes_as_string_view());
+}
+
 // 12.1.2 AvailableCalendars ( ), https://tc39.es/proposal-temporal/#sec-availablecalendars
 // 1.1.1 AvailableCalendars ( ), https://tc39.es/proposal-intl-era-monthcode/#sup-availablecalendars
 Vector<String> const& available_calendars()
@@ -318,7 +324,8 @@ ThrowCompletionOr<MonthCode> parse_month_code(VM& vm, Value argument)
     if (!month_code.is_string())
         return vm.throw_completion<TypeError>(ErrorType::NotAString, month_code);
 
-    return parse_month_code(vm, month_code.as_string().utf8_string());
+    auto month_code_string = month_code.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16();
+    return parse_month_code(vm, month_code_string.bytes_as_string_view());
 }
 
 // 12.2.1 ParseMonthCode ( argument ), https://tc39.es/proposal-temporal/#sec-temporal-parsemonthcode
@@ -388,7 +395,7 @@ ThrowCompletionOr<CalendarFields> prepare_calendar_fields(VM& vm, String const&
             // v. Else if Conversion is TO-STRING, then
             case CalendarFieldConversion::ToString:
                 // 1. Set value to ? ToString(value).
-                set_field_value(key, result, TRY(value.to_string(vm)));
+                set_field_value(key, result, TRY(value.to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16());
                 break;
             // vi. Else if Conversion is TO-TEMPORAL-TIME-ZONE-IDENTIFIER, then
             case CalendarFieldConversion::ToTemporalTimeZoneIdentifier:
@@ -797,7 +804,7 @@ ThrowCompletionOr<String> to_temporal_calendar_identifier(VM& vm, Value temporal
         return vm.throw_completion<TypeError>(ErrorType::TemporalInvalidCalendar);
 
     // 3. Let identifier be ? ParseTemporalCalendarString(temporalCalendarLike).
-    auto identifier = TRY(parse_temporal_calendar_string(vm, temporal_calendar_like.as_string().utf8_string()));
+    auto identifier = TRY(parse_temporal_calendar_string(vm, temporal_calendar_like.as_string().utf16_string_view()));
 
     // 4. Return ? CanonicalizeCalendar(identifier).
     return TRY(canonicalize_calendar(vm, identifier));
diff --git a/Libraries/LibJS/Runtime/Temporal/Calendar.h b/Libraries/LibJS/Runtime/Temporal/Calendar.h
index 2157be4f46..5836e8ba4e 100644
--- a/Libraries/LibJS/Runtime/Temporal/Calendar.h
+++ b/Libraries/LibJS/Runtime/Temporal/Calendar.h
@@ -11,6 +11,7 @@
 
 #include <AK/Optional.h>
 #include <AK/String.h>
+#include <AK/Utf16View.h>
 #include <AK/Vector.h>
 #include <LibJS/Forward.h>
 #include <LibJS/Runtime/Completion.h>
@@ -97,6 +98,7 @@ struct BalancedDate {
 };
 
 ThrowCompletionOr<String> canonicalize_calendar(VM&, StringView id);
+ThrowCompletionOr<String> canonicalize_calendar(VM&, Utf16View id);
 Vector<String> const& available_calendars();
 
 ThrowCompletionOr<MonthCode> parse_month_code(VM&, Value argument);
diff --git a/Libraries/LibJS/Runtime/Temporal/Duration.cpp b/Libraries/LibJS/Runtime/Temporal/Duration.cpp
index 922c4f9df3..5265ddd18c 100644
--- a/Libraries/LibJS/Runtime/Temporal/Duration.cpp
+++ b/Libraries/LibJS/Runtime/Temporal/Duration.cpp
@@ -361,7 +361,7 @@ ThrowCompletionOr<GC::Ref<Duration>> to_temporal_duration(VM& vm, Value item)
             return vm.throw_completion<TypeError>(ErrorType::NotAString, item);
 
         // b. Return ? ParseTemporalDurationString(item).
-        return TRY(parse_temporal_duration_string(vm, item.as_string().utf8_string()));
+        return TRY(parse_temporal_duration_string(vm, item.as_string().utf16_string_view()));
     }
 
     // 3. Let result be a new Partial Duration Record with each field set to 0.
diff --git a/Libraries/LibJS/Runtime/Temporal/ISO8601.cpp b/Libraries/LibJS/Runtime/Temporal/ISO8601.cpp
index a9a192e81b..86f61f6bfe 100644
--- a/Libraries/LibJS/Runtime/Temporal/ISO8601.cpp
+++ b/Libraries/LibJS/Runtime/Temporal/ISO8601.cpp
@@ -74,16 +74,16 @@ static bool is_valid_date(ParseResult const& result)
 // 13.31 RFC 9557 / ISO 8601 grammar, https://tc39.es/proposal-temporal/#sec-temporal-iso8601grammar
 class ISO8601Parser {
 public:
-    explicit ISO8601Parser(StringView input)
+    explicit ISO8601Parser(Utf16View input)
         : m_input(input)
         , m_state({
-              .lexer = GenericLexer { input },
+              .lexer = Utf16GenericLexer { input },
               .parse_result = {},
           })
     {
     }
 
-    [[nodiscard]] GenericLexer const& lexer() const { return m_state.lexer; }
+    [[nodiscard]] Utf16GenericLexer const& lexer() const { return m_state.lexer; }
     [[nodiscard]] ParseResult const& parse_result() const { return m_state.parse_result; }
 
     // https://tc39.es/proposal-temporal/#prod-TemporalDateTimeString
@@ -612,8 +612,8 @@ public:
     {
         StateTransaction transaction { *this };
 
-        Optional<StringView> key;
-        Optional<StringView> value;
+        Optional<Utf16View> key;
+        Optional<Utf16View> value;
 
         // Annotation :::
         //     [ AnnotationCriticalFlag[opt] AnnotationKey = AnnotationValue ]
@@ -1070,7 +1070,7 @@ public:
     }
 
     // https://tc39.es/ecma262/#prod-DecimalDigits
-    [[nodiscard]] bool parse_decimal_digits(Separator separator, Optional<StringView>& result)
+    [[nodiscard]] bool parse_decimal_digits(Separator separator, Optional<Utf16View>& result)
     {
         StateTransaction transaction { *this };
 
@@ -1258,7 +1258,7 @@ private:
             return false;
 
         if constexpr (IsSame<T, char>)
-            storage = transaction.parsed_string_view()[0];
+            storage = static_cast<char>(transaction.parsed_string_view().code_unit_at(0));
         else
             storage = transaction.parsed_string_view();
 
@@ -1267,7 +1267,7 @@ private:
     }
 
     struct State {
-        GenericLexer lexer;
+        Utf16GenericLexer lexer;
         ParseResult parse_result;
     };
 
@@ -1286,7 +1286,7 @@ private:
         }
 
         void commit() { m_commit = true; }
-        StringView parsed_string_view() const
+        Utf16View parsed_string_view() const
         {
             return m_parser.m_input.substring_view(m_start_index, m_parser.m_state.lexer.tell() - m_start_index);
         }
@@ -1298,7 +1298,7 @@ private:
         bool m_commit { false };
     };
 
-    StringView m_input;
+    Utf16View m_input;
     State m_state;
 };
 
@@ -1314,7 +1314,7 @@ private:
     __JS_ENUMERATE(TemporalZonedDateTimeString, parse_temporal_zoned_date_time_string) \
     __JS_ENUMERATE(TimeZoneIdentifier, parse_time_zone_identifier)
 
-Optional<ParseResult> parse_iso8601(Production production, StringView input)
+Optional<ParseResult> parse_iso8601(Production production, Utf16View input)
 {
     ISO8601Parser parser { input };
 
@@ -1337,7 +1337,7 @@ Optional<ParseResult> parse_iso8601(Production production, StringView input)
     return parser.parse_result();
 }
 
-Optional<TimeZoneOffset> parse_utc_offset(StringView input, SubMinutePrecision sub_minute_precision)
+Optional<TimeZoneOffset> parse_utc_offset(Utf16View input, SubMinutePrecision sub_minute_precision)
 {
     ISO8601Parser parser { input };
 
diff --git a/Libraries/LibJS/Runtime/Temporal/ISO8601.h b/Libraries/LibJS/Runtime/Temporal/ISO8601.h
index fe8887d856..495675b1aa 100644
--- a/Libraries/LibJS/Runtime/Temporal/ISO8601.h
+++ b/Libraries/LibJS/Runtime/Temporal/ISO8601.h
@@ -8,53 +8,53 @@
 #pragma once
 
 #include <AK/Optional.h>
-#include <AK/StringView.h>
+#include <AK/Utf16View.h>
 #include <AK/Vector.h>
 
 namespace JS::Temporal {
 
 struct Annotation {
     bool critical { false };
-    StringView key;
-    StringView value;
+    Utf16View key;
+    Utf16View value;
 };
 
 struct TimeZoneOffset {
     Optional<char> sign;
-    Optional<StringView> hours;
-    Optional<StringView> minutes;
-    Optional<StringView> seconds;
-    Optional<StringView> fraction;
-    StringView source_text;
+    Optional<Utf16View> hours;
+    Optional<Utf16View> minutes;
+    Optional<Utf16View> seconds;
+    Optional<Utf16View> fraction;
+    Utf16View source_text;
 };
 
 struct ParseResult {
     Optional<char> sign;
 
-    Optional<StringView> date_year;
-    Optional<StringView> date_month;
-    Optional<StringView> date_day;
-    Optional<StringView> time_hour;
-    Optional<StringView> time_minute;
-    Optional<StringView> time_second;
-    Optional<StringView> time_fraction;
+    Optional<Utf16View> date_year;
+    Optional<Utf16View> date_month;
+    Optional<Utf16View> date_day;
+    Optional<Utf16View> time_hour;
+    Optional<Utf16View> time_minute;
+    Optional<Utf16View> time_second;
+    Optional<Utf16View> time_fraction;
     Optional<TimeZoneOffset> date_time_offset;
 
-    Optional<StringView> utc_designator;
-    Optional<StringView> time_zone_identifier;
-    Optional<StringView> time_zone_iana_name;
+    Optional<Utf16View> utc_designator;
+    Optional<Utf16View> time_zone_identifier;
+    Optional<Utf16View> time_zone_iana_name;
     Optional<TimeZoneOffset> time_zone_offset;
 
-    Optional<StringView> duration_years;
-    Optional<StringView> duration_months;
-    Optional<StringView> duration_weeks;
-    Optional<StringView> duration_days;
-    Optional<StringView> duration_hours;
-    Optional<StringView> duration_hours_fraction;
-    Optional<StringView> duration_minutes;
-    Optional<StringView> duration_minutes_fraction;
-    Optional<StringView> duration_seconds;
-    Optional<StringView> duration_seconds_fraction;
+    Optional<Utf16View> duration_years;
+    Optional<Utf16View> duration_months;
+    Optional<Utf16View> duration_weeks;
+    Optional<Utf16View> duration_days;
+    Optional<Utf16View> duration_hours;
+    Optional<Utf16View> duration_hours_fraction;
+    Optional<Utf16View> duration_minutes;
+    Optional<Utf16View> duration_minutes_fraction;
+    Optional<Utf16View> duration_seconds;
+    Optional<Utf16View> duration_seconds_fraction;
 
     Vector<Annotation> annotations;
 };
@@ -72,13 +72,13 @@ enum class Production {
     TimeZoneIdentifier,
 };
 
-Optional<ParseResult> parse_iso8601(Production, StringView);
+Optional<ParseResult> parse_iso8601(Production, Utf16View);
 
 enum class SubMinutePrecision {
     No,
     Yes,
 };
 
-Optional<TimeZoneOffset> parse_utc_offset(StringView, SubMinutePrecision);
+Optional<TimeZoneOffset> parse_utc_offset(Utf16View, SubMinutePrecision);
 
 }
diff --git a/Libraries/LibJS/Runtime/Temporal/Instant.cpp b/Libraries/LibJS/Runtime/Temporal/Instant.cpp
index ad753e667a..d1ec919f3e 100644
--- a/Libraries/LibJS/Runtime/Temporal/Instant.cpp
+++ b/Libraries/LibJS/Runtime/Temporal/Instant.cpp
@@ -111,7 +111,7 @@ ThrowCompletionOr<GC::Ref<Instant>> to_temporal_instant(VM& vm, Value item)
         return vm.throw_completion<TypeError>(ErrorType::TemporalInvalidInstantString, item);
 
     // 3. Let parsed be ? ParseISODateTime(item, « TemporalInstantString »).
-    auto parsed = TRY(parse_iso_date_time(vm, item.as_string().utf8_string(), { { Production::TemporalInstantString } }));
+    auto parsed = TRY(parse_iso_date_time(vm, item.as_string().utf16_string_view(), { { Production::TemporalInstantString } }));
 
     // 4. Assert: Either parsed.[[TimeZone]].[[OffsetString]] is not empty or parsed.[[TimeZone]].[[Z]] is true, but not both.
     auto const& offset_string = parsed.time_zone.offset_string;
diff --git a/Libraries/LibJS/Runtime/Temporal/PlainDate.cpp b/Libraries/LibJS/Runtime/Temporal/PlainDate.cpp
index d9546b80e2..5142c12921 100644
--- a/Libraries/LibJS/Runtime/Temporal/PlainDate.cpp
+++ b/Libraries/LibJS/Runtime/Temporal/PlainDate.cpp
@@ -135,7 +135,7 @@ ThrowCompletionOr<GC::Ref<PlainDate>> to_temporal_date(VM& vm, Value item, Value
         return vm.throw_completion<TypeError>(ErrorType::TemporalInvalidPlainDate);
 
     // 4. Let result be ? ParseISODateTime(item, « TemporalDateTimeString[~Zoned] »).
-    auto result = TRY(parse_iso_date_time(vm, item.as_string().utf8_string(), { { Production::TemporalDateTimeString } }));
+    auto result = TRY(parse_iso_date_time(vm, item.as_string().utf16_string_view(), { { Production::TemporalDateTimeString } }));
 
     // 5. Let calendar be result.[[Calendar]].
     // 6. If calendar is empty, set calendar to "iso8601".
diff --git a/Libraries/LibJS/Runtime/Temporal/PlainDateConstructor.cpp b/Libraries/LibJS/Runtime/Temporal/PlainDateConstructor.cpp
index 5be5d6cabf..30998e8d5f 100644
--- a/Libraries/LibJS/Runtime/Temporal/PlainDateConstructor.cpp
+++ b/Libraries/LibJS/Runtime/Temporal/PlainDateConstructor.cpp
@@ -72,7 +72,7 @@ ThrowCompletionOr<GC::Ref<Object>> PlainDateConstructor::construct(FunctionObjec
         return vm.throw_completion<TypeError>(ErrorType::NotAString, "calendar"sv);
 
     // 7. Set calendar to ? CanonicalizeCalendar(calendar).
-    auto calendar = TRY(canonicalize_calendar(vm, calendar_value.as_string().utf8_string()));
+    auto calendar = TRY(canonicalize_calendar(vm, calendar_value.as_string().utf16_string_view()));
 
     // 8. If IsValidISODate(y, m, d) is false, throw a RangeError exception.
     if (!is_valid_iso_date(year, month, day))
diff --git a/Libraries/LibJS/Runtime/Temporal/PlainDateTime.cpp b/Libraries/LibJS/Runtime/Temporal/PlainDateTime.cpp
index 5ac15f48a6..1cbc378f83 100644
--- a/Libraries/LibJS/Runtime/Temporal/PlainDateTime.cpp
+++ b/Libraries/LibJS/Runtime/Temporal/PlainDateTime.cpp
@@ -175,7 +175,7 @@ ThrowCompletionOr<GC::Ref<PlainDateTime>> to_temporal_date_time(VM& vm, Value it
         return vm.throw_completion<TypeError>(ErrorType::TemporalInvalidPlainDateTime);
 
     // 4. Let result be ? ParseISODateTime(item, « TemporalDateTimeString[~Zoned] »).
-    auto result = TRY(parse_iso_date_time(vm, item.as_string().utf8_string(), { { Production::TemporalDateTimeString } }));
+    auto result = TRY(parse_iso_date_time(vm, item.as_string().utf16_string_view(), { { Production::TemporalDateTimeString } }));
 
     // 5. If result.[[Time]] is START-OF-DAY, let time be MidnightTimeRecord(); else let time be result.[[Time]].
     auto time = result.time.has<ParsedISODateTime::StartOfDay>() ? midnight_time_record() : result.time.get<Time>();
diff --git a/Libraries/LibJS/Runtime/Temporal/PlainDateTimeConstructor.cpp b/Libraries/LibJS/Runtime/Temporal/PlainDateTimeConstructor.cpp
index 2e5695f9a8..7918c93904 100644
--- a/Libraries/LibJS/Runtime/Temporal/PlainDateTimeConstructor.cpp
+++ b/Libraries/LibJS/Runtime/Temporal/PlainDateTimeConstructor.cpp
@@ -101,7 +101,7 @@ ThrowCompletionOr<GC::Ref<Object>> PlainDateTimeConstructor::construct(FunctionO
         return vm.throw_completion<TypeError>(ErrorType::NotAString, "calendar"sv);
 
     // 13. Set calendar to ? CanonicalizeCalendar(calendar).
-    auto calendar = TRY(canonicalize_calendar(vm, calendar_value.as_string().utf8_string()));
+    auto calendar = TRY(canonicalize_calendar(vm, calendar_value.as_string().utf16_string_view()));
 
     // 14. If IsValidISODate(isoYear, isoMonth, isoDay) is false, throw a RangeError exception.
     if (!is_valid_iso_date(iso_year, iso_month, iso_day))
diff --git a/Libraries/LibJS/Runtime/Temporal/PlainMonthDay.cpp b/Libraries/LibJS/Runtime/Temporal/PlainMonthDay.cpp
index f163a00d64..373ce1a59f 100644
--- a/Libraries/LibJS/Runtime/Temporal/PlainMonthDay.cpp
+++ b/Libraries/LibJS/Runtime/Temporal/PlainMonthDay.cpp
@@ -69,7 +69,7 @@ ThrowCompletionOr<GC::Ref<PlainMonthDay>> to_temporal_month_day(VM& vm, Value it
         return vm.throw_completion<TypeError>(ErrorType::TemporalInvalidPlainMonthDay);
 
     // 4. Let result be ? ParseISODateTime(item, « TemporalMonthDayString »).
-    auto parse_result = TRY(parse_iso_date_time(vm, item.as_string().utf8_string(), { { Production::TemporalMonthDayString } }));
+    auto parse_result = TRY(parse_iso_date_time(vm, item.as_string().utf16_string_view(), { { Production::TemporalMonthDayString } }));
 
     // 5. Let calendar be result.[[Calendar]].
     // 6. If calendar is empty, set calendar to "iso8601".
diff --git a/Libraries/LibJS/Runtime/Temporal/PlainMonthDayConstructor.cpp b/Libraries/LibJS/Runtime/Temporal/PlainMonthDayConstructor.cpp
index ad38b221f8..90f07add81 100644
--- a/Libraries/LibJS/Runtime/Temporal/PlainMonthDayConstructor.cpp
+++ b/Libraries/LibJS/Runtime/Temporal/PlainMonthDayConstructor.cpp
@@ -76,7 +76,7 @@ ThrowCompletionOr<GC::Ref<Object>> PlainMonthDayConstructor::construct(FunctionO
         return vm.throw_completion<TypeError>(ErrorType::NotAString, calendar_value);
 
     // 7. Set calendar to ? CanonicalizeCalendar(calendar).
-    auto calendar = TRY(canonicalize_calendar(vm, calendar_value.as_string().utf8_string()));
+    auto calendar = TRY(canonicalize_calendar(vm, calendar_value.as_string().utf16_string_view()));
 
     // 8. Let y be ? ToIntegerWithTruncation(referenceISOYear).
     auto year = TRY(to_integer_with_truncation(vm, reference_iso_year, ErrorType::TemporalInvalidPlainMonthDay));
diff --git a/Libraries/LibJS/Runtime/Temporal/PlainTime.cpp b/Libraries/LibJS/Runtime/Temporal/PlainTime.cpp
index 0319234a82..d59e1833b9 100644
--- a/Libraries/LibJS/Runtime/Temporal/PlainTime.cpp
+++ b/Libraries/LibJS/Runtime/Temporal/PlainTime.cpp
@@ -159,7 +159,7 @@ ThrowCompletionOr<GC::Ref<PlainTime>> to_temporal_time(VM& vm, Value item, Value
             return vm.throw_completion<TypeError>(ErrorType::TemporalInvalidPlainTime);
 
         // b. Let parseResult be ? ParseISODateTime(item, « TemporalTimeString »).
-        auto parse_result = TRY(parse_iso_date_time(vm, item.as_string().utf8_string(), { { Production::TemporalTimeString } }));
+        auto parse_result = TRY(parse_iso_date_time(vm, item.as_string().utf16_string_view(), { { Production::TemporalTimeString } }));
 
         // c. Assert: parseResult.[[Time]] is not START-OF-DAY.
         VERIFY(!parse_result.time.has<ParsedISODateTime::StartOfDay>());
diff --git a/Libraries/LibJS/Runtime/Temporal/PlainYearMonth.cpp b/Libraries/LibJS/Runtime/Temporal/PlainYearMonth.cpp
index 7f3b3f3081..85ef4bf53c 100644
--- a/Libraries/LibJS/Runtime/Temporal/PlainYearMonth.cpp
+++ b/Libraries/LibJS/Runtime/Temporal/PlainYearMonth.cpp
@@ -72,7 +72,7 @@ ThrowCompletionOr<GC::Ref<PlainYearMonth>> to_temporal_year_month(VM& vm, Value
         return vm.throw_completion<TypeError>(ErrorType::TemporalInvalidPlainYearMonth);
 
     // 4. Let result be ? ParseISODateTime(item, « TemporalYearMonthString »).
-    auto parse_result = TRY(parse_iso_date_time(vm, item.as_string().utf8_string(), { { Production::TemporalYearMonthString } }));
+    auto parse_result = TRY(parse_iso_date_time(vm, item.as_string().utf16_string_view(), { { Production::TemporalYearMonthString } }));
 
     // 5. Let calendar be result.[[Calendar]].
     // 6. If calendar is empty, set calendar to "iso8601".
diff --git a/Libraries/LibJS/Runtime/Temporal/PlainYearMonthConstructor.cpp b/Libraries/LibJS/Runtime/Temporal/PlainYearMonthConstructor.cpp
index a44106e631..064301f0e3 100644
--- a/Libraries/LibJS/Runtime/Temporal/PlainYearMonthConstructor.cpp
+++ b/Libraries/LibJS/Runtime/Temporal/PlainYearMonthConstructor.cpp
@@ -76,7 +76,7 @@ ThrowCompletionOr<GC::Ref<Object>> PlainYearMonthConstructor::construct(Function
         return vm.throw_completion<TypeError>(ErrorType::NotAString, "calendar"sv);
 
     // 7. Set calendar to ? CanonicalizeCalendar(calendar).
-    auto calendar = TRY(canonicalize_calendar(vm, calendar_value.as_string().utf8_string()));
+    auto calendar = TRY(canonicalize_calendar(vm, calendar_value.as_string().utf16_string_view()));
 
     // 8. Let ref be ? ToIntegerWithTruncation(referenceISODay).
     auto reference = TRY(to_integer_with_truncation(vm, reference_iso_day, ErrorType::TemporalInvalidPlainYearMonth));
diff --git a/Libraries/LibJS/Runtime/Temporal/TimeZone.cpp b/Libraries/LibJS/Runtime/Temporal/TimeZone.cpp
index d0a093a80a..530c91434a 100644
--- a/Libraries/LibJS/Runtime/Temporal/TimeZone.cpp
+++ b/Libraries/LibJS/Runtime/Temporal/TimeZone.cpp
@@ -7,6 +7,7 @@
  */
 
 #include <AK/NeverDestroyed.h>
+#include <AK/Utf16String.h>
 #include <LibJS/Runtime/AbstractOperations.h>
 #include <LibJS/Runtime/Date.h>
 #include <LibJS/Runtime/Intl/AbstractOperations.h>
@@ -216,11 +217,11 @@ ThrowCompletionOr<String> to_temporal_time_zone_identifier(VM& vm, Value tempora
     if (!temporal_time_zone_like.is_string())
         return vm.throw_completion<TypeError>(ErrorType::TemporalInvalidTimeZoneName, temporal_time_zone_like);
 
-    return to_temporal_time_zone_identifier(vm, temporal_time_zone_like.as_string().utf8_string());
+    return to_temporal_time_zone_identifier(vm, temporal_time_zone_like.as_string().utf16_string_view());
 }
 
 // 11.1.8 ToTemporalTimeZoneIdentifier ( temporalTimeZoneLike ), https://tc39.es/proposal-temporal/#sec-temporal-totemporaltimezoneidentifier
-ThrowCompletionOr<String> to_temporal_time_zone_identifier(VM& vm, StringView temporal_time_zone_like)
+ThrowCompletionOr<String> to_temporal_time_zone_identifier(VM& vm, Utf16View temporal_time_zone_like)
 {
     // 3. Let parseResult be ? ParseTemporalTimeZoneString(temporalTimeZoneLike).
     auto parse_result = TRY(parse_temporal_time_zone_string(vm, temporal_time_zone_like));
@@ -480,8 +481,10 @@ bool time_zone_equals(StringView one, StringView two)
 
     // NB: IsOffsetTimeZoneIdentifier simply invokes parse_utc_offset and returns whether it has a value. We do this
     //     manually here so that we can handle the offset minutes assertion below without any extra performance penalty.
-    auto time_zone_offset_one = parse_utc_offset(one, SubMinutePrecision::No);
-    auto time_zone_offset_two = parse_utc_offset(two, SubMinutePrecision::No);
+    auto utf16_one = Utf16String::from_utf8(one);
+    auto utf16_two = Utf16String::from_utf8(two);
+    auto time_zone_offset_one = parse_utc_offset(utf16_one, SubMinutePrecision::No);
+    auto time_zone_offset_two = parse_utc_offset(utf16_two, SubMinutePrecision::No);
 
     // 2. If IsOffsetTimeZoneIdentifier(one) is false and IsOffsetTimeZoneIdentifier(two) is false, then
     if (!time_zone_offset_one.has_value() && !time_zone_offset_two.has_value()) {
@@ -524,7 +527,8 @@ ThrowCompletionOr<ParsedTimeZoneIdentifier> parse_time_zone_identifier(VM& vm, S
         return *result;
 
     // 1. Let parseResult be ParseText(StringToCodePoints(identifier), TimeZoneIdentifier).
-    auto parse_result = parse_iso8601(Production::TimeZoneIdentifier, identifier);
+    auto utf16_identifier = Utf16String::from_utf8(identifier);
+    auto parse_result = parse_iso8601(Production::TimeZoneIdentifier, utf16_identifier);
 
     // 2. If parseResult is a List of errors, throw a RangeError exception.
     if (!parse_result.has_value())
@@ -536,13 +540,19 @@ ThrowCompletionOr<ParsedTimeZoneIdentifier> parse_time_zone_identifier(VM& vm, S
     return result;
 }
 
+ThrowCompletionOr<ParsedTimeZoneIdentifier> parse_time_zone_identifier(VM& vm, Utf16View identifier)
+{
+    return parse_time_zone_identifier(vm, identifier.to_utf8_but_should_be_ported_to_utf16());
+}
+
 // 11.1.16 ParseTimeZoneIdentifier ( identifier ), https://tc39.es/proposal-temporal/#sec-parsetimezoneidentifier
 ParsedTimeZoneIdentifier const& parse_time_zone_identifier(String const& identifier)
 {
     // OPTIMIZATION: Some callers can assume that parsing will succeed.
     return time_zone_id_cache().ensure(identifier, [&]() {
         // 1. Let parseResult be ParseText(StringToCodePoints(identifier), TimeZoneIdentifier).
-        auto parse_result = parse_iso8601(Production::TimeZoneIdentifier, identifier);
+        auto utf16_identifier = Utf16String::from_utf8(identifier);
+        auto parse_result = parse_iso8601(Production::TimeZoneIdentifier, utf16_identifier);
         VERIFY(parse_result.has_value());
 
         return parse_time_zone_identifier(*parse_result);
@@ -560,7 +570,7 @@ ParsedTimeZoneIdentifier parse_time_zone_identifier(ParseResult const& parse_res
         // b. NOTE: name is syntactically valid, but does not necessarily conform to IANA Time Zone Database naming
         //    guidelines or correspond with an available named time zone identifier.
         // c. Return Time Zone Identifier Parse Record { [[Name]]: CodePointsToString(name), [[OffsetMinutes]]: EMPTY }.
-        return ParsedTimeZoneIdentifier { .name = String::from_utf8_without_validation(parse_result.time_zone_iana_name->bytes()), .offset_minutes = {} };
+        return ParsedTimeZoneIdentifier { .name = parse_result.time_zone_iana_name->to_utf8_but_should_be_ported_to_utf16(), .offset_minutes = {} };
     }
 
     // 4. Assert: parseResult contains a UTCOffset[~SubMinutePrecision] Parse Node.
@@ -568,7 +578,7 @@ ParsedTimeZoneIdentifier parse_time_zone_identifier(ParseResult const& parse_res
 
     // 5. Let offset be the source text matched by the UTCOffset[~SubMinutePrecision] Parse Node contained within parseResult.
     // 6. Let offsetNanoseconds be ! ParseDateTimeUTCOffset(CodePointsToString(offset)).
-    auto offset_nanoseconds = parse_date_time_utc_offset(parse_result.time_zone_offset->source_text);
+    auto offset_nanoseconds = parse_date_time_utc_offset(*parse_result.time_zone_offset);
 
     // 7. Let offsetMinutes be offsetNanoseconds / (60 × 10**9).
     auto offset_minutes = offset_nanoseconds / 60'000'000'000;
diff --git a/Libraries/LibJS/Runtime/Temporal/TimeZone.h b/Libraries/LibJS/Runtime/Temporal/TimeZone.h
index 0653757fe3..23bc18430a 100644
--- a/Libraries/LibJS/Runtime/Temporal/TimeZone.h
+++ b/Libraries/LibJS/Runtime/Temporal/TimeZone.h
@@ -28,13 +28,14 @@ String format_date_time_utc_offset_rounded(i64 offset_nanoseconds);
 ThrowCompletionOr<String> to_temporal_time_zone_identifier(VM&, Value temporal_time_zone_like);
 i64 get_offset_nanoseconds_for(String const& time_zone, Crypto::SignedBigInteger const& epoch_nanoseconds);
 ISODateTime get_iso_date_time_for(String const& time_zone, Crypto::SignedBigInteger const& epoch_nanoseconds);
-ThrowCompletionOr<String> to_temporal_time_zone_identifier(VM&, StringView temporal_time_zone_like);
+ThrowCompletionOr<String> to_temporal_time_zone_identifier(VM&, Utf16View temporal_time_zone_like);
 ThrowCompletionOr<Crypto::SignedBigInteger> get_epoch_nanoseconds_for(VM&, String const& time_zone, ISODateTime const&, Disambiguation);
 ThrowCompletionOr<Crypto::SignedBigInteger> disambiguate_possible_epoch_nanoseconds(VM&, Vector<Crypto::SignedBigInteger> possible_epoch_ns, String const& time_zone, ISODateTime const&, Disambiguation);
 ThrowCompletionOr<Vector<Crypto::SignedBigInteger>> get_possible_epoch_nanoseconds(VM&, String const& time_zone, ISODateTime const&);
 ThrowCompletionOr<Crypto::SignedBigInteger> get_start_of_day(VM&, String const& time_zone, ISODate);
 bool time_zone_equals(StringView one, StringView two);
 ThrowCompletionOr<ParsedTimeZoneIdentifier> parse_time_zone_identifier(VM&, String const& identifier);
+ThrowCompletionOr<ParsedTimeZoneIdentifier> parse_time_zone_identifier(VM&, Utf16View identifier);
 ParsedTimeZoneIdentifier const& parse_time_zone_identifier(String const& identifier);
 ParsedTimeZoneIdentifier parse_time_zone_identifier(ParseResult const&);
 
diff --git a/Libraries/LibJS/Runtime/Temporal/ZonedDateTime.cpp b/Libraries/LibJS/Runtime/Temporal/ZonedDateTime.cpp
index 3c70770178..c1b3914fc7 100644
--- a/Libraries/LibJS/Runtime/Temporal/ZonedDateTime.cpp
+++ b/Libraries/LibJS/Runtime/Temporal/ZonedDateTime.cpp
@@ -6,6 +6,7 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <AK/Utf16String.h>
 #include <LibJS/Runtime/AbstractOperations.h>
 #include <LibJS/Runtime/Date.h>
 #include <LibJS/Runtime/Temporal/Calendar.h>
@@ -213,7 +214,7 @@ ThrowCompletionOr<GC::Ref<ZonedDateTime>> to_temporal_zoned_date_time(VM& vm, Va
             return vm.throw_completion<TypeError>(ErrorType::TemporalInvalidZonedDateTimeString, item);
 
         // b. Let result be ? ParseISODateTime(item, « TemporalDateTimeString[+Zoned] »).
-        auto result = TRY(parse_iso_date_time(vm, item.as_string().utf8_string(), { { Production::TemporalZonedDateTimeString } }));
+        auto result = TRY(parse_iso_date_time(vm, item.as_string().utf16_string_view(), { { Production::TemporalZonedDateTimeString } }));
 
         // c. Let annotation be result.[[TimeZone]].[[TimeZoneAnnotation]].
         auto annotation = move(result.time_zone.time_zone_annotation);
@@ -222,7 +223,8 @@ ThrowCompletionOr<GC::Ref<ZonedDateTime>> to_temporal_zoned_date_time(VM& vm, Va
         VERIFY(annotation.has_value());
 
         // e. Let timeZone be ? ToTemporalTimeZoneIdentifier(annotation).
-        time_zone = TRY(to_temporal_time_zone_identifier(vm, *annotation));
+        auto utf16_annotation = Utf16String::from_utf8(*annotation);
+        time_zone = TRY(to_temporal_time_zone_identifier(vm, utf16_annotation));
 
         // f. Let offsetString be result.[[TimeZone]].[[OffsetString]].
         offset_string = move(result.time_zone.offset_string);
@@ -246,7 +248,8 @@ ThrowCompletionOr<GC::Ref<ZonedDateTime>> to_temporal_zoned_date_time(VM& vm, Va
         // l. If offsetString is not EMPTY, then
         if (offset_string.has_value()) {
             // i. Let offsetParseResult be ParseText(StringToCodePoints(offsetString), UTCOffset[+SubMinutePrecision]).
-            auto offset_parse_result = parse_utc_offset(*offset_string, SubMinutePrecision::Yes);
+            auto utf16_offset_string = Utf16String::from_utf8(*offset_string);
+            auto offset_parse_result = parse_utc_offset(utf16_offset_string, SubMinutePrecision::Yes);
 
             // ii. Assert: offsetParseResult is a Parse Node.
             VERIFY(offset_parse_result.has_value());
diff --git a/Libraries/LibJS/Runtime/Temporal/ZonedDateTimeConstructor.cpp b/Libraries/LibJS/Runtime/Temporal/ZonedDateTimeConstructor.cpp
index 4879823503..2232c8adc6 100644
--- a/Libraries/LibJS/Runtime/Temporal/ZonedDateTimeConstructor.cpp
+++ b/Libraries/LibJS/Runtime/Temporal/ZonedDateTimeConstructor.cpp
@@ -69,7 +69,7 @@ ThrowCompletionOr<GC::Ref<Object>> ZonedDateTimeConstructor::construct(FunctionO
         return vm.throw_completion<TypeError>(ErrorType::NotAString, time_zone_value);
 
     // 5. Let timeZoneParse be ? ParseTimeZoneIdentifier(timeZone).
-    auto time_zone_parse = TRY(parse_time_zone_identifier(vm, time_zone_value.as_string().utf8_string()));
+    auto time_zone_parse = TRY(parse_time_zone_identifier(vm, time_zone_value.as_string().utf16_string_view()));
 
     String time_zone;
 
@@ -100,7 +100,7 @@ ThrowCompletionOr<GC::Ref<Object>> ZonedDateTimeConstructor::construct(FunctionO
         return vm.throw_completion<TypeError>(ErrorType::NotAString, calendar_value);
 
     // 10. Set calendar to ? CanonicalizeCalendar(calendar).
-    auto calendar = TRY(canonicalize_calendar(vm, calendar_value.as_string().utf8_string()));
+    auto calendar = TRY(canonicalize_calendar(vm, calendar_value.as_string().utf16_string_view()));
 
     // 11. Return ? CreateTemporalZonedDateTime(epochNanoseconds, timeZone, calendar, NewTarget).
     return TRY(create_temporal_zoned_date_time(vm, epoch_nanoseconds, move(time_zone), move(calendar), new_target));
diff --git a/Libraries/LibJS/Runtime/Uint8Array.cpp b/Libraries/LibJS/Runtime/Uint8Array.cpp
index 01b53ad884..685b964266 100644
--- a/Libraries/LibJS/Runtime/Uint8Array.cpp
+++ b/Libraries/LibJS/Runtime/Uint8Array.cpp
@@ -116,7 +116,7 @@ JS_DEFINE_NATIVE_FUNCTION(Uint8ArrayConstructorHelpers::from_base64)
     }
 
     // 9. Let result be FromBase64(string, alphabet, lastChunkHandling).
-    auto result = JS::from_base64(vm, string_value.as_string().utf8_string(), alphabet, last_chunk_handling);
+    auto result = JS::from_base64(vm, string_value.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16(), alphabet, last_chunk_handling);
 
     // 10. If result.[[Error]] is not NONE, then
     if (result.error.has_value()) {
@@ -152,7 +152,7 @@ JS_DEFINE_NATIVE_FUNCTION(Uint8ArrayConstructorHelpers::from_hex)
         return vm.throw_completion<TypeError>(ErrorType::NotAString, string_value);
 
     // 2. Let result be FromHex(string).
-    auto result = JS::from_hex(vm, string_value.as_string().utf8_string());
+    auto result = JS::from_hex(vm, string_value.as_string().utf16_string_view());
 
     // 3. If result.[[Error]] is not NONE, then
     if (result.error.has_value()) {
@@ -220,7 +220,7 @@ JS_DEFINE_NATIVE_FUNCTION(Uint8ArrayPrototypeHelpers::set_from_base64)
     auto byte_length = typed_array_length(typed_array_record);
 
     // 14. Let result be FromBase64(string, alphabet, lastChunkHandling, byteLength).
-    auto result = JS::from_base64(vm, string_value.as_string().utf8_string(), alphabet, last_chunk_handling, byte_length);
+    auto result = JS::from_base64(vm, string_value.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16(), alphabet, last_chunk_handling, byte_length);
 
     // 15. Let bytes be result.[[Bytes]].
     auto bytes = move(result.bytes);
@@ -280,7 +280,7 @@ JS_DEFINE_NATIVE_FUNCTION(Uint8ArrayPrototypeHelpers::set_from_hex)
     auto byte_length = typed_array_length(typed_array_record);
 
     // 7. Let result be FromHex(string, byteLength).
-    auto result = JS::from_hex(vm, string_value.as_string().utf8_string(), byte_length);
+    auto result = JS::from_hex(vm, string_value.as_string().utf16_string_view(), byte_length);
 
     // 8. Let bytes be result.[[Bytes]].
     auto bytes = move(result.bytes);
@@ -524,14 +524,14 @@ DecodeResult from_base64(VM& vm, StringView string, Alphabet alphabet, AK::LastC
 }
 
 // 23.3.3.8 FromHex ( string [ , maxLength ] ), https://tc39.es/ecma262/#sec-fromhex
-DecodeResult from_hex(VM& vm, StringView string, Optional<size_t> max_length)
+DecodeResult from_hex(VM& vm, Utf16View string, Optional<size_t> max_length)
 {
     // 1. If maxLength is not present, set maxLength to 2**53 - 1.
     if (!max_length.has_value())
         max_length = MAX_ARRAY_LIKE_INDEX;
 
     // 2. Let length be the length of string.
-    auto length = string.length();
+    auto length = string.length_in_code_units();
 
     // 3. Let bytes be a new empty List.
     ByteBuffer bytes;
diff --git a/Libraries/LibJS/Runtime/Uint8Array.h b/Libraries/LibJS/Runtime/Uint8Array.h
index fd5021021a..3b6cbf295f 100644
--- a/Libraries/LibJS/Runtime/Uint8Array.h
+++ b/Libraries/LibJS/Runtime/Uint8Array.h
@@ -10,6 +10,7 @@
 #include <AK/ByteBuffer.h>
 #include <AK/Optional.h>
 #include <AK/StringView.h>
+#include <AK/Utf16View.h>
 #include <LibGC/Ptr.h>
 #include <LibJS/Forward.h>
 #include <LibJS/Runtime/Completion.h>
@@ -53,6 +54,6 @@ ThrowCompletionOr<ByteBuffer> get_uint8_array_bytes(VM&, TypedArrayBase const&);
 ThrowCompletionOr<ReadonlyBytes> get_uint8_array_bytes_view(VM&, TypedArrayBase const&);
 void set_uint8_array_bytes(TypedArrayBase&, ReadonlyBytes);
 DecodeResult from_base64(VM&, StringView string, Alphabet alphabet, AK::LastChunkHandling last_chunk_handling, Optional<size_t> max_length = {});
-DecodeResult from_hex(VM&, StringView string, Optional<size_t> max_length = {});
+DecodeResult from_hex(VM&, Utf16View string, Optional<size_t> max_length = {});
 
 }
diff --git a/Libraries/LibJS/Runtime/Value.cpp b/Libraries/LibJS/Runtime/Value.cpp
index 752bda803e..64e8f996b9 100644
--- a/Libraries/LibJS/Runtime/Value.cpp
+++ b/Libraries/LibJS/Runtime/Value.cpp
@@ -7,6 +7,7 @@
  */
 
 #include <AK/AllOf.h>
+#include <AK/Array.h>
 #include <AK/Assertions.h>
 #include <AK/ByteString.h>
 #include <AK/CharacterTypes.h>
@@ -426,7 +427,7 @@ String Value::to_string_without_side_effects() const
     case INT32_TAG:
         return String::number(as_i32());
     case STRING_TAG:
-        return as_string().utf8_string();
+        return as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16();
     case SYMBOL_TAG:
         return as_symbol().descriptive_string().to_utf8_but_should_be_ported_to_utf16();
     case BIGINT_TAG:
@@ -487,55 +488,10 @@ ThrowCompletionOr<GC::Ref<PrimitiveString>> Value::to_primitive_string(VM& vm)
     return PrimitiveString::create(vm, move(string));
 }
 
-// 7.1.17 ToString ( argument ), https://tc39.es/ecma262/#sec-tostring
-ThrowCompletionOr<String> Value::to_string(VM& vm) const
-{
-    if (is_double())
-        return number_to_string(m_value.as_double);
-
-    switch (m_value.tag) {
-    // 1. If argument is a String, return argument.
-    case STRING_TAG:
-        return as_string().utf8_string();
-    // 2. If argument is a Symbol, throw a TypeError exception.
-    case SYMBOL_TAG:
-        return vm.throw_completion<TypeError>(ErrorType::Convert, "symbol", "string");
-    // 3. If argument is undefined, return "undefined".
-    case UNDEFINED_TAG:
-        return "undefined"_string;
-    // 4. If argument is null, return "null".
-    case NULL_TAG:
-        return "null"_string;
-    // 5. If argument is true, return "true".
-    // 6. If argument is false, return "false".
-    case BOOLEAN_TAG:
-        return as_bool() ? "true"_string : "false"_string;
-    // 7. If argument is a Number, return Number::toString(argument, 10).
-    case INT32_TAG:
-        return String::number(as_i32());
-    // 8. If argument is a BigInt, return BigInt::toString(argument, 10).
-    case BIGINT_TAG:
-        return TRY_OR_THROW_OOM(vm, as_bigint().big_integer().to_base(10));
-    // 9. Assert: argument is an Object.
-    case OBJECT_TAG: {
-        // 10. Let primValue be ? ToPrimitive(argument, string).
-        auto primitive_value = TRY(to_primitive(vm, PreferredType::String));
-
-        // 11. Assert: primValue is not an Object.
-        VERIFY(!primitive_value.is_object());
-
-        // 12. Return ? ToString(primValue).
-        return primitive_value.to_string(vm);
-    }
-    default:
-        VERIFY_NOT_REACHED();
-    }
-}
-
 // 7.1.17 ToString ( argument ), https://tc39.es/ecma262/#sec-tostring
 ThrowCompletionOr<ByteString> Value::to_byte_string(VM& vm) const
 {
-    return TRY(to_string(vm)).to_byte_string();
+    return TRY(to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16().to_byte_string();
 }
 
 // 7.1.17 ToString ( argument ), https://tc39.es/ecma262/#sec-tostring
@@ -746,17 +702,47 @@ constexpr bool is_ascii_number(u32 code_point)
     return is_ascii_digit(code_point) || code_point == '.' || (code_point == 'e' || code_point == 'E') || code_point == '+' || code_point == '-';
 }
 
+static constexpr AK::Array js_whitespace_code_units {
+    u'\u0009',
+    u'\u000A',
+    u'\u000B',
+    u'\u000C',
+    u'\u000D',
+    u'\u0020',
+    u'\u00A0',
+    u'\u1680',
+    u'\u2000',
+    u'\u2001',
+    u'\u2002',
+    u'\u2003',
+    u'\u2004',
+    u'\u2005',
+    u'\u2006',
+    u'\u2007',
+    u'\u2008',
+    u'\u2009',
+    u'\u200A',
+    u'\u2028',
+    u'\u2029',
+    u'\u202F',
+    u'\u205F',
+    u'\u3000',
+    u'\uFEFF',
+};
+
+static constexpr Utf16View js_whitespace { js_whitespace_code_units.data(), js_whitespace_code_units.size() };
+
 struct NumberParseResult {
-    StringView literal;
+    Utf16View literal;
     u8 base;
 };
 
-static Optional<NumberParseResult> parse_number_text(StringView text)
+static Optional<NumberParseResult> parse_number_text(Utf16View text)
 {
     NumberParseResult result {};
 
-    auto check_prefix = [&](auto lower_prefix, auto upper_prefix) {
-        if (text.length() <= 2)
+    auto check_prefix = [&](Utf16View lower_prefix, Utf16View upper_prefix) {
+        if (text.length_in_code_units() <= 2)
             return false;
         if (!text.starts_with(lower_prefix) && !text.starts_with(upper_prefix))
             return false;
@@ -794,10 +780,10 @@ static Optional<NumberParseResult> parse_number_text(StringView text)
 }
 
 // 7.1.4.1.1 StringToNumber ( str ), https://tc39.es/ecma262/#sec-stringtonumber
-double string_to_number(StringView string)
+double string_to_number(Utf16View string)
 {
     // 1. Let text be StringToCodePoints(str).
-    auto text = Utf8View(string).trim(whitespace_characters, AK::TrimMode::Both).as_string();
+    auto text = string.trim(js_whitespace);
 
     // 2. Let literal be ParseText(text, StringNumericLiteral).
     if (text.is_empty())
@@ -815,7 +801,7 @@ double string_to_number(StringView string)
 
     // 4. Return StringNumericValue of literal.
     if (result->base != 10) {
-        auto bigint = MUST(Crypto::UnsignedBigInteger::from_base(result->base, result->literal));
+        auto bigint = MUST(Crypto::UnsignedBigInteger::from_base(result->base, result->literal.to_utf8_but_should_be_ported_to_utf16()));
         return bigint.to_double();
     }
 
@@ -852,7 +838,7 @@ ThrowCompletionOr<Value> Value::to_number_slow_case(VM& vm) const
         return Value(as_bool() ? 1 : 0);
     // 6. If argument is a String, return StringToNumber(argument).
     case STRING_TAG:
-        return string_to_number(as_string().utf8_string());
+        return string_to_number(as_string().utf16_string_view());
     // 7. Assert: argument is an Object.
     case OBJECT_TAG: {
         // 8. Let primValue be ? ToPrimitive(argument, number).
@@ -869,7 +855,7 @@ ThrowCompletionOr<Value> Value::to_number_slow_case(VM& vm) const
     }
 }
 
-static Optional<BigInt*> string_to_bigint(VM& vm, StringView string);
+static Optional<BigInt*> string_to_bigint(VM& vm, Utf16View string);
 
 // 7.1.13 ToBigInt ( argument ), https://tc39.es/ecma262/#sec-tobigint
 ThrowCompletionOr<GC::Ref<BigInt>> Value::to_bigint(VM& vm) const
@@ -906,7 +892,7 @@ ThrowCompletionOr<GC::Ref<BigInt>> Value::to_bigint(VM& vm) const
         return primitive.as_bigint();
     case STRING_TAG: {
         // 1. Let n be ! StringToBigInt(prim).
-        auto bigint = string_to_bigint(vm, primitive.as_string().utf8_string());
+        auto bigint = string_to_bigint(vm, primitive.as_string().utf16_string_view());
 
         // 2. If n is undefined, throw a SyntaxError exception.
         if (!bigint.has_value())
@@ -925,17 +911,17 @@ ThrowCompletionOr<GC::Ref<BigInt>> Value::to_bigint(VM& vm) const
 }
 
 struct BigIntParseResult {
-    StringView literal;
+    Utf16View literal;
     u8 base { 10 };
     bool is_negative { false };
 };
 
-static Optional<BigIntParseResult> parse_bigint_text(StringView text)
+static Optional<BigIntParseResult> parse_bigint_text(Utf16View text)
 {
     BigIntParseResult result {};
 
-    auto parse_for_prefixed_base = [&](auto lower_prefix, auto upper_prefix, auto validator) {
-        if (text.length() <= 2)
+    auto parse_for_prefixed_base = [&](Utf16View lower_prefix, Utf16View upper_prefix, auto validator) {
+        if (text.length_in_code_units() <= 2)
             return false;
         if (!text.starts_with(lower_prefix) && !text.starts_with(upper_prefix))
             return false;
@@ -970,10 +956,10 @@ static Optional<BigIntParseResult> parse_bigint_text(StringView text)
 }
 
 // 7.1.14 StringToBigInt ( str ), https://tc39.es/ecma262/#sec-stringtobigint
-static Optional<BigInt*> string_to_bigint(VM& vm, StringView string)
+static Optional<BigInt*> string_to_bigint(VM& vm, Utf16View string)
 {
     // 1. Let text be StringToCodePoints(str).
-    auto text = Utf8View(string).trim(whitespace_characters, AK::TrimMode::Both).as_string();
+    auto text = string.trim(js_whitespace);
 
     // 2. Let literal be ParseText(text, StringIntegerLiteral).
     auto result = parse_bigint_text(text);
@@ -984,7 +970,7 @@ static Optional<BigInt*> string_to_bigint(VM& vm, StringView string)
 
     // 4. Let mv be the MV of literal.
     // 5. Assert: mv is an integer.
-    auto bigint = MUST(Crypto::SignedBigInteger::from_base(result->base, result->literal));
+    auto bigint = MUST(Crypto::SignedBigInteger::from_base(result->base, result->literal.to_utf8_but_should_be_ported_to_utf16()));
     if (result->is_negative && (bigint != bigint_zero()))
         bigint.negate();
 
@@ -2431,7 +2417,7 @@ ThrowCompletionOr<bool> is_loosely_equal(VM& vm, Value lhs, Value rhs)
     // 7. If Type(x) is BigInt and Type(y) is String, then
     if (lhs.is_bigint() && rhs.is_string()) {
         // a. Let n be StringToBigInt(y).
-        auto bigint = string_to_bigint(vm, rhs.as_string().utf8_string());
+        auto bigint = string_to_bigint(vm, rhs.as_string().utf16_string_view());
 
         // b. If n is undefined, return false.
         if (!bigint.has_value())
@@ -2530,7 +2516,7 @@ ThrowCompletionOr<TriState> is_less_than(VM& vm, Value lhs, Value rhs, bool left
     // a. If px is a BigInt and py is a String, then
     if (x_primitive.is_bigint() && y_primitive.is_string()) {
         // i. Let ny be StringToBigInt(py).
-        auto y_bigint = string_to_bigint(vm, y_primitive.as_string().utf8_string());
+        auto y_bigint = string_to_bigint(vm, y_primitive.as_string().utf16_string_view());
 
         // ii. If ny is undefined, return undefined.
         if (!y_bigint.has_value())
@@ -2545,7 +2531,7 @@ ThrowCompletionOr<TriState> is_less_than(VM& vm, Value lhs, Value rhs, bool left
     // b. If px is a String and py is a BigInt, then
     if (x_primitive.is_string() && y_primitive.is_bigint()) {
         // i. Let nx be StringToBigInt(px).
-        auto x_bigint = string_to_bigint(vm, x_primitive.as_string().utf8_string());
+        auto x_bigint = string_to_bigint(vm, x_primitive.as_string().utf16_string_view());
 
         // ii. If nx is undefined, return undefined.
         if (!x_bigint.has_value())
diff --git a/Libraries/LibJS/Runtime/Value.h b/Libraries/LibJS/Runtime/Value.h
index 0703597dfa..5ffcf05fdf 100644
--- a/Libraries/LibJS/Runtime/Value.h
+++ b/Libraries/LibJS/Runtime/Value.h
@@ -18,6 +18,7 @@
 #include <AK/SourceLocation.h>
 #include <AK/String.h>
 #include <AK/Types.h>
+#include <AK/Utf16View.h>
 #include <LibGC/NanBoxedValue.h>
 #include <LibGC/Ptr.h>
 #include <LibGC/Root.h>
@@ -401,7 +402,6 @@ public:
 
     u64 encoded() const { return m_value.encoded; }
 
-    ThrowCompletionOr<String> to_string(VM&) const;
     ThrowCompletionOr<ByteString> to_byte_string(VM&) const;
     ThrowCompletionOr<Utf16String> to_utf16_string(VM&) const;
     ThrowCompletionOr<GC::Ref<PrimitiveString>> to_primitive_string(VM&);
@@ -597,7 +597,7 @@ JS_API void number_to_string(StringBuilder&, double, NumberToStringMode = Number
 [[nodiscard]] JS_API String number_to_string(double, NumberToStringMode = NumberToStringMode::WithExponent);
 [[nodiscard]] JS_API Utf16String number_to_utf16_string(double, NumberToStringMode = NumberToStringMode::WithExponent);
 [[nodiscard]] ByteString number_to_byte_string(double, NumberToStringMode = NumberToStringMode::WithExponent);
-double string_to_number(StringView);
+double string_to_number(Utf16View);
 
 inline bool Value::operator==(Value const& value) const { return same_value(*this, value); }
 
diff --git a/Libraries/LibJS/Runtime/ValueTraits.h b/Libraries/LibJS/Runtime/ValueTraits.h
index 9dd8fc3f09..e851bd2628 100644
--- a/Libraries/LibJS/Runtime/ValueTraits.h
+++ b/Libraries/LibJS/Runtime/ValueTraits.h
@@ -19,7 +19,7 @@ struct ValueTraits : public Traits<Value> {
     {
         VERIFY(!value.is_special_empty_value());
         if (value.is_string())
-            return value.as_string().utf8_string().hash();
+            return value.as_string().utf16_string_view().hash();
 
         if (value.is_bigint())
             return value.as_bigint().big_integer().hash();
diff --git a/Libraries/LibTest/JavaScriptTestRunner.h b/Libraries/LibTest/JavaScriptTestRunner.h
index 00c80bfe10..3dd71afa79 100644
--- a/Libraries/LibTest/JavaScriptTestRunner.h
+++ b/Libraries/LibTest/JavaScriptTestRunner.h
@@ -208,7 +208,7 @@ inline JS_DEFINE_NATIVE_FUNCTION(TestRunnerGlobalObject::report_test)
         return JS::js_undefined();
 
     auto test_name_value = vm.argument(0);
-    auto test_name = TRY(test_name_value.to_string(vm));
+    auto test_name = TRY(test_name_value.to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16();
     auto state_value = vm.argument(1);
     self.on_test_reported(test_name, state_value);
     return JS::js_undefined();
@@ -293,7 +293,7 @@ inline Vector<ByteString> TestRunner::get_test_paths() const
 inline void print_test_timings(String test_name, JS::Value state_value)
 {
     if (state_value.is_string()) {
-        auto state_string = state_value.as_string().utf8_string();
+        auto state_string = state_value.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16();
         if (state_string == "pass"sv) {
             print_modifiers({ FG_BOLD });
             out("Finished: ");
diff --git a/Libraries/LibWeb/Animations/KeyframeEffect.cpp b/Libraries/LibWeb/Animations/KeyframeEffect.cpp
index 668e3d2677..9244ff8a05 100644
--- a/Libraries/LibWeb/Animations/KeyframeEffect.cpp
+++ b/Libraries/LibWeb/Animations/KeyframeEffect.cpp
@@ -69,26 +69,26 @@ static WebIDL::ExceptionOr<KeyframeType<AL>> process_a_keyframe_like_object(JS::
             return Optional<double> {};
         auto double_value = TRY(value.to_double(vm));
         if (isnan(double_value) || isinf(double_value))
-            return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, MUST(String::formatted("Invalid offset value: {}", TRY(value.to_string(vm)))) };
+            return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, MUST(String::formatted("Invalid offset value: {}", TRY(value.to_utf16_string(vm)))) };
         return double_value;
     };
 
     Function<WebIDL::ExceptionOr<String>(JS::Value)> to_string = [&vm](JS::Value value) -> WebIDL::ExceptionOr<String> {
-        return TRY(value.to_string(vm));
+        return TRY(value.to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16();
     };
 
     Function<WebIDL::ExceptionOr<Bindings::CompositeOperationOrAuto>(JS::Value)> to_composite_operation = [&vm](JS::Value value) -> WebIDL::ExceptionOr<Bindings::CompositeOperationOrAuto> {
         if (value.is_undefined())
             return Bindings::CompositeOperationOrAuto::Auto;
 
-        auto string_value = TRY(value.to_string(vm));
-        if (string_value == "replace")
+        auto string_value = TRY(value.to_utf16_string(vm));
+        if (string_value == "replace"sv)
             return Bindings::CompositeOperationOrAuto::Replace;
-        if (string_value == "add")
+        if (string_value == "add"sv)
             return Bindings::CompositeOperationOrAuto::Add;
-        if (string_value == "accumulate")
+        if (string_value == "accumulate"sv)
             return Bindings::CompositeOperationOrAuto::Accumulate;
-        if (string_value == "auto")
+        if (string_value == "auto"sv)
             return Bindings::CompositeOperationOrAuto::Auto;
 
         return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, "Invalid composite value"sv };
@@ -158,7 +158,7 @@ static WebIDL::ExceptionOr<KeyframeType<AL>> process_a_keyframe_like_object(JS::
         if (!input_property.is_string())
             continue;
 
-        auto name = input_property.as_string().utf8_string();
+        auto name = input_property.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16();
 
         // Handle the two special cases
         if (name == "cssFloat"sv || name == "cssOffset"sv) {
@@ -204,7 +204,7 @@ static WebIDL::ExceptionOr<KeyframeType<AL>> process_a_keyframe_like_object(JS::
         else {
             // Let property values be the result of converting raw value to a DOMString using the procedure for
             // converting an ECMAScript value to a DOMString [WEBIDL].
-            property_values = TRY(raw_value.to_string(vm));
+            property_values = TRY(raw_value.to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16();
         }
 
         // 4. Calculate the normalized property name as the result of applying the IDL attribute name to animation
diff --git a/Libraries/LibWeb/Bindings/AudioConstructor.cpp b/Libraries/LibWeb/Bindings/AudioConstructor.cpp
index 88c469b76b..f61d00b54c 100644
--- a/Libraries/LibWeb/Bindings/AudioConstructor.cpp
+++ b/Libraries/LibWeb/Bindings/AudioConstructor.cpp
@@ -61,7 +61,7 @@ JS::ThrowCompletionOr<GC::Ref<JS::Object>> AudioConstructor::construct(FunctionO
     // 4. If src is given, then set an attribute value for audio using "src" and src.
     //    (This will cause the user agent to invoke the object's resource selection algorithm before returning.)
     if (!src_value.is_undefined()) {
-        auto src = TRY(src_value.to_string(vm));
+        auto src = TRY(src_value.to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16();
         audio->set_attribute_value(HTML::AttributeNames::src, move(src));
     }
 
diff --git a/Libraries/LibWeb/Bindings/MainThreadVM.cpp b/Libraries/LibWeb/Bindings/MainThreadVM.cpp
index 2e567f4fce..bcf67bc0e4 100644
--- a/Libraries/LibWeb/Bindings/MainThreadVM.cpp
+++ b/Libraries/LibWeb/Bindings/MainThreadVM.cpp
@@ -402,7 +402,7 @@ void initialize_main_thread_vm(AgentType type)
             auto specifier = vm.argument(0);
 
             // 1. Set specifier to ? ToString(specifier).
-            auto specifier_string = TRY(specifier.to_string(vm));
+            auto specifier_string = TRY(specifier.to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16();
 
             // 2. Let url be the result of resolving a module specifier given moduleScript and specifier.
             auto url = TRY(Bindings::throw_dom_exception_if_needed(vm, [&] {
diff --git a/Libraries/LibWeb/Bindings/OptionConstructor.cpp b/Libraries/LibWeb/Bindings/OptionConstructor.cpp
index 2ada473410..93daf6ee20 100644
--- a/Libraries/LibWeb/Bindings/OptionConstructor.cpp
+++ b/Libraries/LibWeb/Bindings/OptionConstructor.cpp
@@ -72,7 +72,7 @@ JS::ThrowCompletionOr<GC::Ref<JS::Object>> OptionConstructor::construct(Function
 
     // 4. If value is given, then set an attribute value for option using "value" and value.
     if (!vm.argument(1).is_undefined()) {
-        auto value = TRY(vm.argument(1).to_string(vm));
+        auto value = TRY(vm.argument(1).to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16();
         option_element->set_attribute_value(HTML::AttributeNames::value, value);
     }
 
diff --git a/Libraries/LibWeb/CSS/CSSFontFeatureValuesMap.cpp b/Libraries/LibWeb/CSS/CSSFontFeatureValuesMap.cpp
index 16025be435..ababf0d8bc 100644
--- a/Libraries/LibWeb/CSS/CSSFontFeatureValuesMap.cpp
+++ b/Libraries/LibWeb/CSS/CSSFontFeatureValuesMap.cpp
@@ -73,7 +73,7 @@ OrderedHashMap<FlyString, Vector<u32>> CSSFontFeatureValuesMap::to_ordered_hash_
     OrderedHashMap<FlyString, Vector<u32>> result;
 
     for (auto const& entry : *m_map_entries) {
-        auto key = MUST(entry.key.to_string(vm()));
+        auto key = MUST(entry.key.to_utf16_string(vm())).to_utf8_but_should_be_ported_to_utf16();
 
         auto const& array = as<JS::Array>(entry.value.as_object());
         auto array_length = MUST(MUST(array.get(vm().names.length)).to_length(vm()));
diff --git a/Libraries/LibWeb/CSS/CSSUnparsedValue.cpp b/Libraries/LibWeb/CSS/CSSUnparsedValue.cpp
index 23b0702041..1a5ae4ff15 100644
--- a/Libraries/LibWeb/CSS/CSSUnparsedValue.cpp
+++ b/Libraries/LibWeb/CSS/CSSUnparsedValue.cpp
@@ -90,7 +90,7 @@ static WebIDL::ExceptionOr<CSSUnparsedSegment> unparsed_segment_from_js_value(JS
 {
     if (auto variable_reference = value.as_if<CSSVariableReferenceValue>())
         return GC::Ref { *variable_reference };
-    return TRY(value.to_string(vm));
+    return TRY(value.to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16();
 }
 
 // https://drafts.css-houdini.org/css-typed-om-1/#ref-for-dfn-set-the-value-of-an-existing-indexed-property
diff --git a/Libraries/LibWeb/Clipboard/Clipboard.cpp b/Libraries/LibWeb/Clipboard/Clipboard.cpp
index 2c9838c57f..34c18ebfd2 100644
--- a/Libraries/LibWeb/Clipboard/Clipboard.cpp
+++ b/Libraries/LibWeb/Clipboard/Clipboard.cpp
@@ -456,7 +456,7 @@ GC::Ref<WebIDL::Promise> Clipboard::write(GC::RootVector<GC::Ref<ClipboardItem>>
                             // 1. If v is a DOMString, then follow the below steps:
                             if (value.is_string()) {
                                 // 1. Let dataAsBytes be the result of UTF-8 encoding v.
-                                auto const& data_as_bytes = value.as_string().utf8_string();
+                                auto const& data_as_bytes = value.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16();
 
                                 // 2. Let blobData be a Blob created using dataAsBytes with its type set to representation’s MIME type.
                                 auto blob_data = FileAPI::Blob::create(realm, MUST(ByteBuffer::copy(data_as_bytes.bytes())), move(mime_type));
diff --git a/Libraries/LibWeb/Clipboard/ClipboardItem.cpp b/Libraries/LibWeb/Clipboard/ClipboardItem.cpp
index a5c24473c9..59549438a9 100644
--- a/Libraries/LibWeb/Clipboard/ClipboardItem.cpp
+++ b/Libraries/LibWeb/Clipboard/ClipboardItem.cpp
@@ -144,7 +144,7 @@ WebIDL::ExceptionOr<GC::Ref<WebIDL::Promise>> ClipboardItem::get_type(String con
                     // 1. If v is a DOMString, then follow the below steps:
                     if (value.is_string()) {
                         // 1. Let dataAsBytes be the result of UTF-8 encoding v.
-                        auto utf8_string = value.as_string().utf8_string();
+                        auto utf8_string = value.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16();
                         auto data_as_bytes = MUST(ByteBuffer::copy(utf8_string.bytes()));
 
                         // 2. Let blobData be a Blob created using dataAsBytes with its type set to mimeType, serialized.
diff --git a/Libraries/LibWeb/Crypto/CryptoAlgorithms.cpp b/Libraries/LibWeb/Crypto/CryptoAlgorithms.cpp
index 1459e94445..69fade855a 100644
--- a/Libraries/LibWeb/Crypto/CryptoAlgorithms.cpp
+++ b/Libraries/LibWeb/Crypto/CryptoAlgorithms.cpp
@@ -51,7 +51,7 @@ static JS::ThrowCompletionOr<HashAlgorithmIdentifier> hash_algorithm_identifier_
 
     auto maybe_normalized_algorithm = [&]() -> WebIDL::ExceptionOr<NormalizedAlgorithmAndParameter> {
         if (hash_value.is_string()) {
-            auto const hash_string = TRY(hash_value.to_string(vm));
+            auto const hash_string = TRY(hash_value.to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16();
             return normalize_an_algorithm(*realm, hash_string, "digest"_string);
         }
         if (hash_value.is_object()) {
@@ -520,7 +520,7 @@ JS::ThrowCompletionOr<NonnullOwnPtr<AlgorithmParams>> EcKeyGenParams::from_value
     auto& object = value.as_object();
 
     auto curve_value = TRY(object.get("namedCurve"_utf16_fly_string));
-    auto curve = TRY(curve_value.to_string(vm));
+    auto curve = TRY(curve_value.to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16();
 
     return adopt_own<AlgorithmParams>(*new EcKeyGenParams { curve });
 }
@@ -574,7 +574,7 @@ JS::ThrowCompletionOr<NonnullOwnPtr<AlgorithmParams>> EcKeyImportParams::from_va
     auto& object = value.as_object();
 
     auto named_curve_value = TRY(object.get("namedCurve"_utf16_fly_string));
-    auto named_curve = TRY(named_curve_value.to_string(vm));
+    auto named_curve = TRY(named_curve_value.to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16();
 
     return adopt_own<AlgorithmParams>(*new EcKeyImportParams { named_curve });
 }
diff --git a/Libraries/LibWeb/Crypto/CryptoAlgorithms.h b/Libraries/LibWeb/Crypto/CryptoAlgorithms.h
index 0444677d09..a168e24639 100644
--- a/Libraries/LibWeb/Crypto/CryptoAlgorithms.h
+++ b/Libraries/LibWeb/Crypto/CryptoAlgorithms.h
@@ -51,7 +51,7 @@ struct HashAlgorithmIdentifier : public AlgorithmIdentifier {
             [](String const& name) -> JS::ThrowCompletionOr<String> { return name; },
             [&](GC::Root<JS::Object> const& obj) -> JS::ThrowCompletionOr<String> {
                 auto name_property = TRY(obj->get("name"_utf16_fly_string));
-                return name_property.to_string(vm);
+                return TRY(name_property.to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16();
             });
 
         return value;
diff --git a/Libraries/LibWeb/Crypto/CryptoKey.cpp b/Libraries/LibWeb/Crypto/CryptoKey.cpp
index a8e5ff8d8e..753d1f646e 100644
--- a/Libraries/LibWeb/Crypto/CryptoKey.cpp
+++ b/Libraries/LibWeb/Crypto/CryptoKey.cpp
@@ -447,7 +447,7 @@ String CryptoKey::algorithm_name() const
 {
     if (m_algorithm_name.is_empty()) {
         auto name = MUST(m_algorithm_cached->get("name"_utf16_fly_string));
-        m_algorithm_name = MUST(name.to_string(vm()));
+        m_algorithm_name = MUST(name.to_utf16_string(vm())).to_utf8_but_should_be_ported_to_utf16();
     }
     return m_algorithm_name;
 }
diff --git a/Libraries/LibWeb/Crypto/SubtleCrypto.cpp b/Libraries/LibWeb/Crypto/SubtleCrypto.cpp
index 8ce8df6d84..6e19b8a0b9 100644
--- a/Libraries/LibWeb/Crypto/SubtleCrypto.cpp
+++ b/Libraries/LibWeb/Crypto/SubtleCrypto.cpp
@@ -134,7 +134,7 @@ WebIDL::ExceptionOr<NormalizedAlgorithmAndParameter> normalize_an_algorithm(JS::
     }
 
     // 4. Let algName be the value of the name attribute of initialAlg.
-    auto algorithm_name = TRY(initial_algorithm.to_string(vm));
+    auto algorithm_name = TRY(initial_algorithm.to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16();
 
     RegisteredAlgorithm desired_type;
 
diff --git a/Libraries/LibWeb/DOM/Element.cpp b/Libraries/LibWeb/DOM/Element.cpp
index da23181888..28003ca407 100644
--- a/Libraries/LibWeb/DOM/Element.cpp
+++ b/Libraries/LibWeb/DOM/Element.cpp
@@ -3431,7 +3431,7 @@ void Element::enqueue_a_custom_element_callback_reaction(FlyString const& callba
         VERIFY(!arguments.is_empty());
         auto& attribute_name_value = arguments.first();
         VERIFY(attribute_name_value.is_string());
-        auto attribute_name = attribute_name_value.as_string().utf8_string();
+        auto attribute_name = attribute_name_value.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16();
 
         // 2. If definition's observed attributes does not contain attributeName, then return.
         if (!definition->observed_attributes().contains_slow(attribute_name))
diff --git a/Libraries/LibWeb/DOM/EventTarget.cpp b/Libraries/LibWeb/DOM/EventTarget.cpp
index 042eec99f3..39fe1f6191 100644
--- a/Libraries/LibWeb/DOM/EventTarget.cpp
+++ b/Libraries/LibWeb/DOM/EventTarget.cpp
@@ -769,7 +769,7 @@ JS::ThrowCompletionOr<void> EventTarget::process_event_handler_for_event(FlyStri
             // 2. If event's returnValue attribute's value is the empty string, then set event's returnValue attribute's value to return value.
             auto& before_unload_event = static_cast<HTML::BeforeUnloadEvent&>(event);
             if (before_unload_event.return_value().is_empty())
-                before_unload_event.set_return_value(TRY(return_value.to_string(vm())));
+                before_unload_event.set_return_value(TRY(return_value.to_utf16_string(vm())).to_utf8_but_should_be_ported_to_utf16());
         }
     }
 
diff --git a/Libraries/LibWeb/DOMURL/Origin.cpp b/Libraries/LibWeb/DOMURL/Origin.cpp
index 6f44696b5a..3b74b1f4e0 100644
--- a/Libraries/LibWeb/DOMURL/Origin.cpp
+++ b/Libraries/LibWeb/DOMURL/Origin.cpp
@@ -56,7 +56,7 @@ WebIDL::ExceptionOr<GC::Ref<Origin>> Origin::from(JS::VM& vm, JS::Value value)
     }
     // 2. If value is a string:
     else if (value.is_string()) {
-        auto string = value.as_string().utf8_string();
+        auto string = value.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16();
 
         // 1. Let parsedURL be the result of basic URL parsing value.
         auto parsed_url = URL::Parser::basic_parse(string);
diff --git a/Libraries/LibWeb/Encoding/TextEncoderStream.cpp b/Libraries/LibWeb/Encoding/TextEncoderStream.cpp
index 5578383d6f..f5879cfaf7 100644
--- a/Libraries/LibWeb/Encoding/TextEncoderStream.cpp
+++ b/Libraries/LibWeb/Encoding/TextEncoderStream.cpp
@@ -96,15 +96,14 @@ WebIDL::ExceptionOr<void> TextEncoderStream::encode_and_enqueue_chunk(JS::Value
     auto& vm = this->vm();
 
     // 1. Let input be the result of converting chunk to a DOMString.
-    auto input = TRY(chunk.to_string(vm));
+    auto input = TRY(chunk.to_utf16_string(vm));
 
     // 2. Convert input to an I/O queue of code units.
     // Spec Note: DOMString, as well as an I/O queue of code units rather than scalar values, are used here so that a
     //            surrogate pair that is split between chunks can be reassembled into the appropriate scalar value.
     //            The behavior is otherwise identical to USVString. In particular, lone surrogates will be replaced
     //            with U+FFFD.
-    auto code_points = input.code_points();
-    auto it = code_points.begin();
+    size_t code_unit_index = 0;
 
     // 3. Let output be the I/O queue of bytes « end-of-queue ».
     ByteBuffer output;
@@ -113,7 +112,7 @@ WebIDL::ExceptionOr<void> TextEncoderStream::encode_and_enqueue_chunk(JS::Value
     while (true) {
         // 2. If item is end-of-queue, then:
         // NOTE: This is done out-of-order so that we're not dereferencing a code point iterator that points to the end.
-        if (it.done()) {
+        if (code_unit_index >= input.length_in_code_units()) {
             // 1. Convert output into a byte sequence.
             // Note: No-op.
 
@@ -132,10 +131,10 @@ WebIDL::ExceptionOr<void> TextEncoderStream::encode_and_enqueue_chunk(JS::Value
         }
 
         // 1. Let item be the result of reading from input.
-        auto item = *it;
+        auto item = input.code_unit_at(code_unit_index);
 
         // 3. Let result be the result of executing the convert code unit to scalar value algorithm with encoder, item and input.
-        auto result = convert_code_unit_to_scalar_value(item, it);
+        auto result = convert_code_unit_to_scalar_value(item, code_unit_index);
 
         // 4. If result is not continue, then process an item with result, encoder’s encoder, input, output, and "fatal".
         if (result.has_value()) {
@@ -168,10 +167,10 @@ WebIDL::ExceptionOr<void> TextEncoderStream::encode_and_flush()
 }
 
 // https://encoding.spec.whatwg.org/#convert-code-unit-to-scalar-value
-Optional<u32> TextEncoderStream::convert_code_unit_to_scalar_value(u32 item, Utf8CodePointIterator& code_point_iterator)
+Optional<u32> TextEncoderStream::convert_code_unit_to_scalar_value(u32 item, size_t& code_unit_index)
 {
     ArmedScopeGuard move_to_next_code_point_guard = [&] {
-        ++code_point_iterator;
+        ++code_unit_index;
     };
 
     // 1. If encoder’s leading surrogate is non-null, then:
diff --git a/Libraries/LibWeb/Encoding/TextEncoderStream.h b/Libraries/LibWeb/Encoding/TextEncoderStream.h
index 7298feca1c..2d5c24d264 100644
--- a/Libraries/LibWeb/Encoding/TextEncoderStream.h
+++ b/Libraries/LibWeb/Encoding/TextEncoderStream.h
@@ -32,7 +32,7 @@ private:
     WebIDL::ExceptionOr<void> encode_and_enqueue_chunk(JS::Value);
     WebIDL::ExceptionOr<void> encode_and_flush();
 
-    Optional<u32> convert_code_unit_to_scalar_value(u32 item, Utf8CodePointIterator& code_point_iterator);
+    Optional<u32> convert_code_unit_to_scalar_value(u32 item, size_t& code_unit_index);
 
     // https://encoding.spec.whatwg.org/#textencoderstream-pending-high-surrogate
     Optional<u32> m_leading_surrogate;
diff --git a/Libraries/LibWeb/HTML/CustomElements/CustomElementRegistry.cpp b/Libraries/LibWeb/HTML/CustomElements/CustomElementRegistry.cpp
index 0c4d69ec18..8b6aadf447 100644
--- a/Libraries/LibWeb/HTML/CustomElements/CustomElementRegistry.cpp
+++ b/Libraries/LibWeb/HTML/CustomElements/CustomElementRegistry.cpp
@@ -114,7 +114,7 @@ static JS::ThrowCompletionOr<Vector<String>> convert_value_to_sequence_of_string
 
         // 2. Let x be ? ToString(V).
         // 3. Return the IDL DOMString value that represents the same sequence of code units as the one the ECMAScript String value x represents.
-        auto string_value = TRY(next_item.to_string(vm));
+        auto string_value = TRY(next_item.to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16();
 
         sequence_of_strings.append(move(string_value));
 
diff --git a/Libraries/LibWeb/HTML/DOMStringMap.cpp b/Libraries/LibWeb/HTML/DOMStringMap.cpp
index eddc1589a7..0dfb4df69b 100644
--- a/Libraries/LibWeb/HTML/DOMStringMap.cpp
+++ b/Libraries/LibWeb/HTML/DOMStringMap.cpp
@@ -130,7 +130,7 @@ WebIDL::ExceptionOr<void> DOMStringMap::set_value_of_new_named_property(String c
 {
     // NOTE: Since PlatformObject does not know the type of value, we must convert it ourselves.
     //       The type of `value` is `DOMString`.
-    auto value = TRY(unconverted_value.to_string(vm()));
+    auto value = TRY(unconverted_value.to_utf16_string(vm())).to_utf8_but_should_be_ported_to_utf16();
 
     StringBuilder builder;
 
diff --git a/Libraries/LibWeb/HTML/HTMLInputElement.cpp b/Libraries/LibWeb/HTML/HTMLInputElement.cpp
index 4285bc0a62..032d7e80a9 100644
--- a/Libraries/LibWeb/HTML/HTMLInputElement.cpp
+++ b/Libraries/LibWeb/HTML/HTMLInputElement.cpp
@@ -1400,7 +1400,7 @@ void HTMLInputElement::create_range_input_shadow_tree()
             auto key_value = MUST(vm.argument(0).get(vm, "key"_utf16_fly_string));
             if (!key_value.is_string())
                 return JS::js_undefined();
-            auto key = key_value.as_string().utf8_string();
+            auto key = key_value.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16();
 
             if (key == "ArrowLeft" || key == "ArrowDown")
                 MUST(step_down());
diff --git a/Libraries/LibWeb/HTML/Navigable.cpp b/Libraries/LibWeb/HTML/Navigable.cpp
index 5ef119bb77..db8f6c0ba5 100644
--- a/Libraries/LibWeb/HTML/Navigable.cpp
+++ b/Libraries/LibWeb/HTML/Navigable.cpp
@@ -2625,7 +2625,7 @@ GC::Ptr<DOM::Document> Navigable::evaluate_javascript_url(URL::URL const& url, U
 
     // 9. If evaluationStatus is a normal completion, and evaluationStatus.[[Value]] is a String, then set result to evaluationStatus.[[Value]].
     if (evaluation_status.type() == JS::Completion::Type::Normal && evaluation_status.value().is_string()) {
-        result = evaluation_status.value().as_string().utf8_string();
+        result = evaluation_status.value().as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16();
     } else {
         // 10. Otherwise, return null.
         return nullptr;
diff --git a/Libraries/LibWeb/HTML/Scripting/ImportMap.cpp b/Libraries/LibWeb/HTML/Scripting/ImportMap.cpp
index b6e5fabc17..fe6ed9bb76 100644
--- a/Libraries/LibWeb/HTML/Scripting/ImportMap.cpp
+++ b/Libraries/LibWeb/HTML/Scripting/ImportMap.cpp
@@ -164,7 +164,7 @@ WebIDL::ExceptionOr<ModuleSpecifierMap> sort_and_normalise_module_specifier_map(
         }
 
         // 4. Let addressURL be the result of resolving a URL-like module specifier given value and baseURL.
-        auto address_url = resolve_url_like_module_specifier(value.as_string().utf8_string(), base_url);
+        auto address_url = resolve_url_like_module_specifier(value.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16(), base_url);
 
         // 5. If addressURL is null, then:
         if (!address_url.has_value()) {
@@ -282,7 +282,7 @@ WebIDL::ExceptionOr<ModuleIntegrityMap> normalize_module_integrity_map(JS::Realm
         }
 
         // 4. Set normalized[resolvedURL] to value.
-        normalized.set(resolved_url.release_value(), value.as_string().utf8_string());
+        normalized.set(resolved_url.release_value(), value.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16());
     }
 
     // 3. Return normalized.
diff --git a/Libraries/LibWeb/HTML/Storage.cpp b/Libraries/LibWeb/HTML/Storage.cpp
index 5c215a7369..0be5ac09c5 100644
--- a/Libraries/LibWeb/HTML/Storage.cpp
+++ b/Libraries/LibWeb/HTML/Storage.cpp
@@ -294,7 +294,7 @@ WebIDL::ExceptionOr<void> Storage::set_value_of_named_property(String const& key
 {
     // NOTE: Since PlatformObject does not know the type of value, we must convert it ourselves.
     //       The type of `value` is `DOMString`.
-    auto value = TRY(unconverted_value.to_string(vm()));
+    auto value = TRY(unconverted_value.to_utf16_string(vm())).to_utf8_but_should_be_ported_to_utf16();
     return set_item(key, value);
 }
 
diff --git a/Libraries/LibWeb/HTML/StructuredSerialize.cpp b/Libraries/LibWeb/HTML/StructuredSerialize.cpp
index c1b1588b6d..6538f5396e 100644
--- a/Libraries/LibWeb/HTML/StructuredSerialize.cpp
+++ b/Libraries/LibWeb/HTML/StructuredSerialize.cpp
@@ -302,7 +302,7 @@ public:
             serialized.encode(MUST(value.as_bigint().big_integer().to_base(10)));
         } else if (value.is_string()) {
             serialized.encode(ValueTag::StringPrimitive);
-            serialized.encode(value.as_string().utf8_string());
+            serialized.encode(value.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16());
         } else {
             return_primitive_type = false;
         }
@@ -338,7 +338,7 @@ public:
             // 10. Otherwise, if value has a [[StringData]] internal slot, then set serialized to { [[Type]]: "String", [[StringData]]: value.[[StringData]] }.
             else if (auto const* string_object = as_if<JS::StringObject>(*object)) {
                 serialized.encode(ValueTag::StringObject);
-                serialized.encode(string_object->primitive_string().utf8_string());
+                serialized.encode(string_object->primitive_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16());
             }
 
             // 11. Otherwise, if value has a [[DateValue]] internal slot, then set serialized to { [[Type]]: "Date", [[DateValue]]: value.[[DateValue]] }.
@@ -397,7 +397,7 @@ public:
                 // 2. If name is not one of "Error", "EvalError", "RangeError", "ReferenceError", "SyntaxError", "TypeError", or "URIError", then set name to "Error".
                 auto type = ErrorType::Error;
                 if (name.is_string())
-                    type = error_name_to_type(name.as_string().utf8_string());
+                    type = error_name_to_type(name.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16());
 
                 // 3. Let valueMessageDesc be ? value.[[GetOwnProperty]]("message").
                 auto value_message_descriptor = TRY(object->internal_get_own_property(m_vm.names.message));
diff --git a/Libraries/LibWeb/IndexedDB/Internal/Algorithms.cpp b/Libraries/LibWeb/IndexedDB/Internal/Algorithms.cpp
index 86bf0b7cf5..6a3721667d 100644
--- a/Libraries/LibWeb/IndexedDB/Internal/Algorithms.cpp
+++ b/Libraries/LibWeb/IndexedDB/Internal/Algorithms.cpp
@@ -293,7 +293,7 @@ WebIDL::ExceptionOr<GC::Ref<Key>> convert_a_value_to_a_key(JS::Realm& realm, JS:
     if (input.is_string()) {
 
         // 1. Return a new key with type string and value input.
-        return Key::create_string(realm, input.as_string().utf8_string());
+        return Key::create_string(realm, input.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16());
     }
 
     // - If input is a buffer source type
@@ -2496,14 +2496,14 @@ WebIDL::ExceptionOr<GC::Ref<IDBRequest>> create_a_request_to_retrieve_multiple_i
         count = TRY(TRY(query_or_options.get(vm, "count"_utf16)).to_u32(vm));
 
         // 3. Set direction to query_or_options["direction"].
-        auto direction_value = TRY(TRY(query_or_options.get(vm, "direction"_utf16)).to_string(vm));
-        if (direction_value == "next")
+        auto direction_value = TRY(TRY(query_or_options.get(vm, "direction"_utf16)).to_utf16_string(vm));
+        if (direction_value == "next"sv)
             direction = Bindings::IDBCursorDirection::Next;
-        else if (direction_value == "nextunique")
+        else if (direction_value == "nextunique"sv)
             direction = Bindings::IDBCursorDirection::Nextunique;
-        else if (direction_value == "prev")
+        else if (direction_value == "prev"sv)
             direction = Bindings::IDBCursorDirection::Prev;
-        else if (direction_value == "prevunique")
+        else if (direction_value == "prevunique"sv)
             direction = Bindings::IDBCursorDirection::Prevunique;
     }
 
diff --git a/Libraries/LibWeb/Infra/JSON.cpp b/Libraries/LibWeb/Infra/JSON.cpp
index 9271d9c9a1..fbd6328658 100644
--- a/Libraries/LibWeb/Infra/JSON.cpp
+++ b/Libraries/LibWeb/Infra/JSON.cpp
@@ -50,7 +50,7 @@ WebIDL::ExceptionOr<String> serialize_javascript_value_to_json_string(JS::VM& vm
     VERIFY(result.is_string());
 
     // 4. Return result.
-    return result.as_string().utf8_string();
+    return result.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16();
 }
 
 // https://infra.spec.whatwg.org/#serialize-a-javascript-value-to-json-bytes
@@ -154,7 +154,7 @@ String serialize_an_infra_value_to_a_json_string(JS::Realm& realm, JSONTopLevel
     //            whitespace inserted.
     auto result = MUST(JS::call(vm, *realm.intrinsics().json_stringify_function(), JS::js_undefined(), js_value));
     VERIFY(result.is_string());
-    return result.as_string().utf8_string();
+    return result.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16();
 }
 
 // https://infra.spec.whatwg.org/#serialize-a-javascript-value-to-json-bytes
diff --git a/Libraries/LibWeb/WebDriver/Contexts.cpp b/Libraries/LibWeb/WebDriver/Contexts.cpp
index 99f0d8ffff..669b6977fc 100644
--- a/Libraries/LibWeb/WebDriver/Contexts.cpp
+++ b/Libraries/LibWeb/WebDriver/Contexts.cpp
@@ -77,7 +77,7 @@ ErrorOr<GC::Ref<HTML::WindowProxy>, WebDriver::Error> deserialize_web_frame(JS::
         return WebDriver::Error::from_code(WebDriver::ErrorCode::InvalidArgument, "Object is not a web frame"sv);
 
     // 2. Let reference be the result of getting the web frame identifier property from object.
-    auto reference = property.value().as_string().utf8_string();
+    auto reference = property.value().as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16();
 
     // 3. Let browsing context be the browsing context whose window handle is reference, or null if no such browsing
     //    context exists.
@@ -112,7 +112,7 @@ ErrorOr<GC::Ref<HTML::WindowProxy>, WebDriver::Error> deserialize_web_window(JS:
         return WebDriver::Error::from_code(WebDriver::ErrorCode::InvalidArgument, "Object is not a web window"sv);
 
     // 2. Let reference be the result of getting the web window identifier property from object.
-    auto reference = property.value().as_string().utf8_string();
+    auto reference = property.value().as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16();
 
     // 3. Let browsing context be the browsing context whose window handle is reference, or null if no such browsing
     //    context exists.
diff --git a/Libraries/LibWeb/WebDriver/ElementReference.cpp b/Libraries/LibWeb/WebDriver/ElementReference.cpp
index 83e2594aaf..2ed5f1fa57 100644
--- a/Libraries/LibWeb/WebDriver/ElementReference.cpp
+++ b/Libraries/LibWeb/WebDriver/ElementReference.cpp
@@ -194,7 +194,7 @@ ErrorOr<GC::Ref<Web::DOM::Element>, WebDriver::Error> deserialize_web_element(We
         return WebDriver::Error::from_code(WebDriver::ErrorCode::InvalidArgument, "Object is not a web element"sv);
 
     // 2. Let reference be the result of getting the web element identifier property from object.
-    auto reference = property.value().as_string().utf8_string();
+    auto reference = property.value().as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16();
 
     // 3. Let element be the result of trying to get a known element with session and reference.
     auto element = TRY(get_known_element(browsing_context, reference));
@@ -490,7 +490,7 @@ ErrorOr<GC::Ref<Web::DOM::ShadowRoot>, WebDriver::Error> deserialize_shadow_root
         return WebDriver::Error::from_code(WebDriver::ErrorCode::InvalidArgument, "Object is not a Shadow Root"sv);
 
     // 2. Let reference be the result of getting the shadow root identifier property from object.
-    auto reference = property.value().as_string().utf8_string();
+    auto reference = property.value().as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16();
 
     // 3. Let shadow be the result of trying to get a known shadow root with session and reference.
     auto shadow = TRY(get_known_shadow_root(browsing_context, reference));
diff --git a/Libraries/LibWeb/WebDriver/JSON.cpp b/Libraries/LibWeb/WebDriver/JSON.cpp
index 25abc613b4..f454862ec7 100644
--- a/Libraries/LibWeb/WebDriver/JSON.cpp
+++ b/Libraries/LibWeb/WebDriver/JSON.cpp
@@ -227,7 +227,7 @@ static Response internal_json_clone(HTML::BrowsingContext const& browsing_contex
     if (value.is_number())
         return JsonValue { value.as_double() };
     if (value.is_string())
-        return JsonValue { value.as_string().utf8_string() };
+        return JsonValue { value.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16() };
 
     // AD-HOC: BigInt and Symbol not mentioned anywhere in the WebDriver spec, as it references ES5.
     //         It assumes that all primitives are handled above, and the value is an object for the remaining steps.
@@ -301,7 +301,7 @@ static Response internal_json_clone(HTML::BrowsingContext const& browsing_contex
         if (!to_json_result.is_string())
             return WebDriver::Error::from_code(ErrorCode::JavascriptError, "toJSON did not return a String"sv);
 
-        return JsonValue { to_json_result.as_string().utf8_string() };
+        return JsonValue { to_json_result.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16() };
     }
 
     // -> Otherwise
diff --git a/Libraries/LibWeb/WebGL/WebGLContextAttributes.cpp b/Libraries/LibWeb/WebGL/WebGLContextAttributes.cpp
index 98f76e3bb4..50e14614a8 100644
--- a/Libraries/LibWeb/WebGL/WebGLContextAttributes.cpp
+++ b/Libraries/LibWeb/WebGL/WebGLContextAttributes.cpp
@@ -99,7 +99,7 @@ JS::ThrowCompletionOr<WebGLContextAttributes> convert_value_to_context_attribute
     Bindings::WebGLPowerPreference power_preference_value { Bindings::WebGLPowerPreference::Default };
 
     if (!power_preference.is_undefined()) {
-        auto power_preference_string = TRY(power_preference.to_string(vm));
+        auto power_preference_string = TRY(power_preference.to_utf16_string(vm));
 
         if (power_preference_string == "high-performance"sv)
             power_preference_value = Bindings::WebGLPowerPreference::HighPerformance;
diff --git a/Libraries/LibWeb/WebIDL/AbstractOperations.cpp b/Libraries/LibWeb/WebIDL/AbstractOperations.cpp
index 6808fb1259..359712406b 100644
--- a/Libraries/LibWeb/WebIDL/AbstractOperations.cpp
+++ b/Libraries/LibWeb/WebIDL/AbstractOperations.cpp
@@ -234,22 +234,23 @@ JS::Completion call_user_object_operation(CallbackType& callback, Utf16FlyString
 JS::ThrowCompletionOr<String> to_byte_string(JS::VM& vm, JS::Value value)
 {
     // 1. Let x be ? ToString(V).
-    auto x = TRY(value.to_string(vm));
+    auto x = TRY(value.to_utf16_string(vm));
 
     // 2. If the value of any element of x is greater than 255, then throw a TypeError.
-    for (auto [i, character] : enumerate(x.code_points())) {
+    for (size_t i = 0; i < x.length_in_code_units(); ++i) {
+        auto character = x.code_unit_at(i);
         if (character > 0xFF)
-            return vm.throw_completion<JS::TypeError>(MUST(String::formatted("Invalid byte 0x{:X} at index {}, must be an integer no less than 0 and no greater than 0xFF", character, x.code_points().byte_offset_of(i))));
+            return vm.throw_completion<JS::TypeError>(MUST(String::formatted("Invalid byte 0x{:X} at index {}, must be an integer no less than 0 and no greater than 0xFF", character, i)));
     }
 
     // 3. Return an IDL ByteString value whose length is the length of x, and where the value of each element is the value of the corresponding element of x.
     // FIXME: This should return a ByteString.
-    return x;
+    return x.to_utf8_but_should_be_ported_to_utf16();
 }
 
 JS::ThrowCompletionOr<String> to_string(JS::VM& vm, JS::Value value)
 {
-    return value.to_string(vm);
+    return TRY(value.to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16();
 }
 
 JS::ThrowCompletionOr<Utf16String> to_utf16_string(JS::VM& vm, JS::Value value)
diff --git a/Meta/Fuzzers/FuzzilliJs.cpp b/Meta/Fuzzers/FuzzilliJs.cpp
index 8d9b8ee1e5..f5e92785b5 100644
--- a/Meta/Fuzzers/FuzzilliJs.cpp
+++ b/Meta/Fuzzers/FuzzilliJs.cpp
@@ -149,8 +149,8 @@ JS_DEFINE_NATIVE_FUNCTION(TestRunnerGlobalObject::fuzzilli)
     if (!vm.argument_count())
         return JS::js_undefined();
 
-    auto operation = TRY(vm.argument(0).to_string(vm));
-    if (operation == "FUZZILLI_CRASH") {
+    auto operation = TRY(vm.argument(0).to_utf16_string(vm));
+    if (operation == "FUZZILLI_CRASH"sv) {
         auto type = TRY(vm.argument(1).to_i32(vm));
         switch (type) {
         case 0:
@@ -160,14 +160,14 @@ JS_DEFINE_NATIVE_FUNCTION(TestRunnerGlobalObject::fuzzilli)
             VERIFY_NOT_REACHED();
             break;
         }
-    } else if (operation == "FUZZILLI_PRINT") {
+    } else if (operation == "FUZZILLI_PRINT"sv) {
         static FILE* fzliout = fdopen(REPRL_DWFD, "w");
         if (!fzliout) {
             dbgln("Fuzzer output not available");
             fzliout = stdout;
         }
 
-        auto string = TRY(vm.argument(1).to_string(vm));
+        auto string = TRY(vm.argument(1).to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16();
         outln(fzliout, "{}", string);
         fflush(fzliout);
     }
diff --git a/Meta/Generators/libweb_bindings/to_idl_value.py b/Meta/Generators/libweb_bindings/to_idl_value.py
index 6816796057..b70ed1b07a 100644
--- a/Meta/Generators/libweb_bindings/to_idl_value.py
+++ b/Meta/Generators/libweb_bindings/to_idl_value.py
@@ -214,7 +214,7 @@ def write_enumeration_conversion(out: TextIO, enumeration: Enumeration, includes
 JS::ThrowCompletionOr<{enumeration.name}> {converter_function_name(enumeration)}(JS::VM& vm, JS::Value value)
 {{
     // 1. Let S be the result of calling ? ToString(V).
-    auto value_as_string = TRY(value.to_string(vm));
+    auto value_as_string = TRY(value.to_utf16_string(vm));
 
     // 2. If S is not one of E’s enumeration values, then throw a TypeError.
     // 3. Return the enumeration value of type E that is equal to S.
@@ -1198,7 +1198,7 @@ def union_to_idl_value(
         includes.add("LibJS/Runtime/ValueInlines.h")
         enumeration_conversion = f"""
         if ({value_name}.is_string()) {{
-            auto enumeration_string = TRY({value_name}.to_string(vm));
+            auto enumeration_string = TRY({value_name}.to_utf16_string(vm));
 """
         for enumeration_type in types.enumeration_types:
             enumeration = context.enumeration(enumeration_type)
diff --git a/Services/WebContent/ConsoleGlobalEnvironmentExtensions.cpp b/Services/WebContent/ConsoleGlobalEnvironmentExtensions.cpp
index ecc6a8524b..d5e495912f 100644
--- a/Services/WebContent/ConsoleGlobalEnvironmentExtensions.cpp
+++ b/Services/WebContent/ConsoleGlobalEnvironmentExtensions.cpp
@@ -69,7 +69,7 @@ JS_DEFINE_NATIVE_FUNCTION(ConsoleGlobalEnvironmentExtensions::$_function)
     auto* console_global_object = TRY(get_console(vm));
     auto& window = *console_global_object->m_window_object;
 
-    auto selector = TRY(vm.argument(0).to_string(vm));
+    auto selector = TRY(vm.argument(0).to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16();
 
     if (vm.argument_count() > 1) {
         auto node = vm.argument(1).as_if<Web::DOM::ParentNode>();
@@ -91,7 +91,7 @@ JS_DEFINE_NATIVE_FUNCTION(ConsoleGlobalEnvironmentExtensions::$$_function)
     auto* console_global_object = TRY(get_console(vm));
     auto& window = *console_global_object->m_window_object;
 
-    auto selector = TRY(vm.argument(0).to_string(vm));
+    auto selector = TRY(vm.argument(0).to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16();
 
     Web::DOM::ParentNode* element = &window.associated_document();
 
diff --git a/Services/WebContent/DevToolsConsoleClient.cpp b/Services/WebContent/DevToolsConsoleClient.cpp
index 910efc578b..587c808a1f 100644
--- a/Services/WebContent/DevToolsConsoleClient.cpp
+++ b/Services/WebContent/DevToolsConsoleClient.cpp
@@ -58,7 +58,7 @@ static JsonValue serialize_js_value(JS::Realm& realm, JS::Value value)
         return value.as_bool();
 
     if (value.is_string())
-        return value.as_string().utf8_string();
+        return value.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16();
 
     if (value.is_number()) {
         if (value.is_nan())
diff --git a/Tests/LibJS/test-bytecode-cache.cpp b/Tests/LibJS/test-bytecode-cache.cpp
index fd4b71ad3f..1f58d72025 100644
--- a/Tests/LibJS/test-bytecode-cache.cpp
+++ b/Tests/LibJS/test-bytecode-cache.cpp
@@ -860,7 +860,7 @@ TEST_CASE(bytecode_cache_to_string_caches_lazy_ascii_source_text)
     auto result = vm->run(script);
     VERIFY(!result.is_throw_completion());
     VERIFY(result.value().is_string());
-    EXPECT_EQ(result.value().as_string().utf8_string(), "function mapped() { return 'hello'; }|function mapped() { return 'hello'; }"_string);
+    EXPECT_EQ(result.value().as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16(), "function mapped() { return 'hello'; }|function mapped() { return 'hello'; }"_string);
     EXPECT_EQ(shared_data.m_source_text_owner.to_utf8(), "function mapped() { return 'hello'; }"sv);
 }
 
@@ -893,7 +893,7 @@ TEST_CASE(bytecode_cache_to_string_uses_lazy_utf8_offset_map)
     auto result = vm->run(script);
     VERIFY(!result.is_throw_completion());
     VERIFY(result.value().is_string());
-    EXPECT_EQ(result.value().as_string().utf8_string(), "function mapped() { return 'Known Trick\xe2\x84\xa2'; }"_string);
+    EXPECT_EQ(result.value().as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16(), "function mapped() { return 'Known Trick\xe2\x84\xa2'; }"_string);
     EXPECT_EQ(shared_data.m_source_text_owner.to_utf8(), "function mapped() { return 'Known Trick\xe2\x84\xa2'; }"sv);
 }
 
@@ -926,7 +926,7 @@ TEST_CASE(bytecode_cache_materializes_from_mapped_blob)
     auto result = vm->run(script_or_error.release_value());
     VERIFY(!result.is_throw_completion());
     VERIFY(result.value().is_string());
-    EXPECT_EQ(result.value().as_string().utf8_string(), "hello"_string);
+    EXPECT_EQ(result.value().as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16(), "hello"_string);
 }
 
 TEST_CASE(fresh_precompiled_function_executables_materialize_lazily)
diff --git a/Tests/LibJS/test-js.cpp b/Tests/LibJS/test-js.cpp
index 187946f0c6..8ca9427c81 100644
--- a/Tests/LibJS/test-js.cpp
+++ b/Tests/LibJS/test-js.cpp
@@ -22,7 +22,7 @@ TESTJS_PROGRAM_FLAG(test262_parser_tests, "Run test262 parser tests", "test262-p
 TESTJS_GLOBAL_FUNCTION(can_parse_source, canParseSource)
 {
     auto& realm = *vm.current_realm();
-    auto source = TRY(vm.argument(0).to_string(vm));
+    auto source = TRY(vm.argument(0).to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16();
     auto script = JS::Script::parse(source, realm);
     return JS::Value(!script.is_error());
 }
@@ -38,7 +38,7 @@ TESTJS_GLOBAL_FUNCTION(evaluate_source, evaluateSource)
 {
     auto& realm = *vm.current_realm();
 
-    auto source = TRY(vm.argument(0).to_string(vm));
+    auto source = TRY(vm.argument(0).to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16();
 
     auto script = JS::Script::parse(source, realm);
     if (script.is_error())
@@ -51,7 +51,7 @@ TESTJS_GLOBAL_FUNCTION(evaluate_module, evaluateModule)
 {
     auto& realm = *vm.current_realm();
 
-    auto path = TRY(vm.argument(0).to_string(vm));
+    auto path = TRY(vm.argument(0).to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16();
     auto module = Test::JS::parse_module(path.to_byte_string(), realm);
     if (module.is_error())
         return vm.throw_completion<JS::SyntaxError>(module.error().error.to_string());
@@ -155,7 +155,7 @@ TESTJS_GLOBAL_FUNCTION(detach_array_buffer, detachArrayBuffer)
 TESTJS_GLOBAL_FUNCTION(set_time_zone, setTimeZone)
 {
     auto current_time_zone = JS::PrimitiveString::create(vm, Core::TimeZone::current_time_zone());
-    auto time_zone = TRY(vm.argument(0).to_string(vm));
+    auto time_zone = TRY(vm.argument(0).to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16();
 
     if (auto result = Core::TimeZone::set_current_time_zone(time_zone); result.is_error())
         return vm.throw_completion<JS::InternalError>(MUST(String::formatted("Could not set time zone: {}", result.error())));
@@ -168,7 +168,7 @@ TESTJS_GLOBAL_FUNCTION(to_utf8_bytes, toUTF8Bytes)
 {
     auto& realm = *vm.current_realm();
 
-    auto string = TRY(vm.argument(0).to_string(vm));
+    auto string = TRY(vm.argument(0).to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16();
     auto typed_array = TRY(JS::Uint8Array::create(realm, string.bytes().size()));
 
     for (auto [i, byte] : enumerate(string.bytes()))
diff --git a/Tests/LibWasm/test-wasm.cpp b/Tests/LibWasm/test-wasm.cpp
index 4f9d380e5b..8c2a297db4 100644
--- a/Tests/LibWasm/test-wasm.cpp
+++ b/Tests/LibWasm/test-wasm.cpp
@@ -23,7 +23,7 @@ TESTJS_GLOBAL_FUNCTION(read_binary_wasm_file, readBinaryWasmFile)
         return StringView { error_string, strlen(error_string) };
     };
 
-    auto filename = TRY(vm.argument(0).to_string(vm));
+    auto filename = TRY(vm.argument(0).to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16();
     auto file = Core::File::open(filename, Core::File::OpenMode::Read);
     if (file.is_error())
         return vm.throw_completion<JS::TypeError>(error_code_to_string(file.error().code()));
@@ -292,7 +292,7 @@ TESTJS_GLOBAL_FUNCTION(test_simd_vector, testSIMDVector)
         if (expect.is_string()) {
             if (element_size != 32 && element_size != 64)
                 return vm.throw_completion<JS::TypeError>("Expected element of size 32 or 64"sv);
-            auto string = expect.as_string().utf8_string();
+            auto string = expect.as_string().utf16_string_view().to_utf8_but_should_be_ported_to_utf16();
             if (string == "nan:canonical") {
                 auto is_canonical = element_size == 32 ? _is_canonical_nan32(got) : _is_canonical_nan64(got);
                 if (!is_canonical)
@@ -323,7 +323,7 @@ void WebAssemblyModule::initialize(JS::Realm& realm)
 
 JS_DEFINE_NATIVE_FUNCTION(WebAssemblyModule::get_export)
 {
-    auto name = TRY(vm.argument(0).to_string(vm));
+    auto name = TRY(vm.argument(0).to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16();
     auto this_value = vm.this_value();
     auto object = TRY(this_value.to_object(vm));
     if (!is<WebAssemblyModule>(*object))
diff --git a/Utilities/js.cpp b/Utilities/js.cpp
index b592cd3d68..5b4a65eaf9 100644
--- a/Utilities/js.cpp
+++ b/Utilities/js.cpp
@@ -287,7 +287,7 @@ static JS::ThrowCompletionOr<JS::Value> load_ini_impl(JS::VM& vm)
 
 static JS::ThrowCompletionOr<JS::Value> load_json_impl(JS::VM& vm)
 {
-    auto filename = TRY(vm.argument(0).to_string(vm));
+    auto filename = TRY(vm.argument(0).to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16();
     auto file_or_error = Core::File::open(filename, Core::File::OpenMode::Read);
     if (file_or_error.is_error())
         return vm.throw_completion<JS::Error>(TRY_OR_THROW_OOM(vm, String::formatted("Failed to open '{}': {}", filename, file_or_error.error())));
@@ -338,7 +338,7 @@ JS_DEFINE_NATIVE_FUNCTION(ReplObject::save_to_file)
 {
     if (!vm.argument_count())
         return JS::Value(false);
-    auto const save_path = TRY(vm.argument(0).to_string(vm));
+    auto const save_path = TRY(vm.argument(0).to_utf16_string(vm)).to_utf8_but_should_be_ported_to_utf16();
     if (!write_to_file(save_path).is_error()) {
         return JS::Value(true);
     }
@@ -788,7 +788,7 @@ static ErrorOr<void> repl(JS::Realm& realm)
 {
     while (s_keep_running_repl) {
         auto const piece = TRY(read_next_piece());
-        if (Utf8View { piece }.trim(JS::whitespace_characters).is_empty())
+        if (Utf16String::from_utf8(piece).trim(JS::whitespace_characters).is_empty())
             continue;
 
         g_repl_statements.append(piece);
diff --git a/Utilities/wasm.cpp b/Utilities/wasm.cpp
index 95e14ffbb1..f961e25aed 100644
--- a/Utilities/wasm.cpp
+++ b/Utilities/wasm.cpp
@@ -304,7 +304,7 @@ static ErrorOr<T, Wasm::Result> trap_for_js_exception(JS::VM& vm, JS::ThrowCompl
 
     auto const& completion = result.error();
     auto& exception = completion.value();
-    warnln("JS exception: {}", MUST(exception.to_string(vm)));
+    warnln("JS exception: {}", MUST(exception.to_utf16_string(vm)));
     return Wasm::Trap { ByteString("JS exception") };
 }