diff --git a/web/CHANGELOG.md b/web/CHANGELOG.md
index 72de9522..7776d4ad 100644
--- a/web/CHANGELOG.md
+++ b/web/CHANGELOG.md
@@ -11,6 +11,7 @@
 - Exposed constants with primitive values as non-`external` so they can be
   `switch`ed over.
 - Add an extension `responseHeaders` to `XMLHttpRequest`.
+- Correctly namespace `WebAssembly` types.
 
 ## 1.0.0
 
diff --git a/web/lib/src/dom/wasm_js_api.dart b/web/lib/src/dom/wasm_js_api.dart
index 2035190f..e8783177 100644
--- a/web/lib/src/dom/wasm_js_api.dart
+++ b/web/lib/src/dom/wasm_js_api.dart
@@ -73,6 +73,7 @@ extension type ModuleImportDescriptor._(JSObject _) implements JSObject {
   external ImportExportKind get kind;
   external set kind(ImportExportKind value);
 }
+@JS('WebAssembly.Module')
 extension type Module._(JSObject _) implements JSObject {
   external factory Module(BufferSource bytes);
 
@@ -83,6 +84,7 @@ extension type Module._(JSObject _) implements JSObject {
     String sectionName,
   );
 }
+@JS('WebAssembly.Instance')
 extension type Instance._(JSObject _) implements JSObject {
   external factory Instance(
     Module module, [
@@ -102,6 +104,7 @@ extension type MemoryDescriptor._(JSObject _) implements JSObject {
   external int get maximum;
   external set maximum(int value);
 }
+@JS('WebAssembly.Memory')
 extension type Memory._(JSObject _) implements JSObject {
   external factory Memory(MemoryDescriptor descriptor);
 
@@ -122,6 +125,7 @@ extension type TableDescriptor._(JSObject _) implements JSObject {
   external int get maximum;
   external set maximum(int value);
 }
+@JS('WebAssembly.Table')
 extension type Table._(JSObject _) implements JSObject {
   external factory Table(
     TableDescriptor descriptor, [
@@ -150,6 +154,7 @@ extension type GlobalDescriptor._(JSObject _) implements JSObject {
   external bool get mutable;
   external set mutable(bool value);
 }
+@JS('WebAssembly.Global')
 extension type Global._(JSObject _) implements JSObject {
   external factory Global(
     GlobalDescriptor descriptor, [
diff --git a/web_generator/CHANGELOG.md b/web_generator/CHANGELOG.md
index d9c47969..69a023a3 100644
--- a/web_generator/CHANGELOG.md
+++ b/web_generator/CHANGELOG.md
@@ -1,3 +1,11 @@
 ## 1.0.0-wip
 
-- Initial separation of `web_generator` from `web`.
\ No newline at end of file
+- Initial separation of `web_generator` from `web`.
+- New IDL interface `RHL` added. `ExtendedAttribute` idl interface updated to
+  expose its `rhs` property and `Interfacelike` idl interface updated to expose
+  `extAttrs` property. The generator now adds a 
+  `JS(LegacyNamespace.$extensionTypeName)` annotation on `JS` objects if
+  they've an IDL extended attribute `[LegacyNamespace=Foo]` defined in their IDL
+  description. 
+
+ 
\ No newline at end of file
diff --git a/web_generator/lib/src/translator.dart b/web_generator/lib/src/translator.dart
index 554ea9b4..d0a2c310 100644
--- a/web_generator/lib/src/translator.dart
+++ b/web_generator/lib/src/translator.dart
@@ -5,6 +5,7 @@
 import 'dart:js_interop';
 
 import 'package:code_builder/code_builder.dart' as code;
+import 'package:collection/collection.dart';
 import 'package:path/path.dart' as p;
 
 import 'banned_names.dart';
@@ -1244,6 +1245,7 @@ class Translator {
   code.ExtensionType _extensionType({
     required String jsName,
     required String dartClassName,
+    required List<idl.ExtendedAttribute> extendedAttributes,
     required MdnInterface? mdnInterface,
     required BCDInterfaceStatus? interfaceStatus,
     required List<String> implements,
@@ -1257,6 +1259,12 @@ class Translator {
 
     final jsObject = _typeReference(_RawType('JSObject', false));
     const representationFieldName = '_';
+    final legacyNameSpace = extendedAttributes
+        .firstWhereOrNull(
+          (extendedAttribute) => extendedAttribute.name == 'LegacyNamespace',
+        )
+        ?.rhs
+        .value;
     final instancePropertyMethods = <code.Method>[];
     final staticPropertyMethods = <code.Method>[];
     final propertySpecs = _properties(properties, mdnInterface);
@@ -1267,7 +1275,12 @@ class Translator {
     return code.ExtensionType((b) => b
       ..docs.addAll(docs)
       ..annotations.addAll(
-          _jsOverride(isObjectLiteral || jsName == dartClassName ? '' : jsName))
+        _jsOverride(
+          legacyNameSpace != null
+              ? '$legacyNameSpace.$jsName'
+              : (isObjectLiteral || jsName == dartClassName ? '' : jsName),
+        ),
+      )
       ..name = dartClassName
       ..primaryConstructorName = '_'
       ..representationDeclaration = code.RepresentationDeclaration((b) => b
@@ -1300,6 +1313,7 @@ class Translator {
     final type = interfacelike.type;
     final isNamespace = type == 'namespace';
     final isDictionary = type == 'dictionary';
+    final extendedAttributes = idlInterfacelike.extAttrs.toDart;
 
     final mdnInterface = docProvider.interfaceFor(jsName);
 
@@ -1327,6 +1341,7 @@ class Translator {
       _extensionType(
         jsName: jsName,
         dartClassName: dartClassName,
+        extendedAttributes: extendedAttributes,
         mdnInterface: mdnInterface,
         interfaceStatus: interfaceStatus,
         implements: implements,
diff --git a/web_generator/lib/src/webidl_api.dart b/web_generator/lib/src/webidl_api.dart
index 676b3334..841d8068 100644
--- a/web_generator/lib/src/webidl_api.dart
+++ b/web_generator/lib/src/webidl_api.dart
@@ -35,6 +35,7 @@ extension type Interfacelike._(JSObject _) implements Named {
   external bool get partial;
   external JSArray<Member> get members;
   external String? get inheritance;
+  external JSArray<ExtendedAttribute> get extAttrs;
 }
 
 extension type Callback._(JSObject _) implements Named {
@@ -66,6 +67,12 @@ extension type Member._(JSObject _) implements JSObject {
 
 extension type ExtendedAttribute._(JSObject _) implements JSObject {
   external String get name;
+  external RHS get rhs;
+}
+
+extension type RHS._(JSObject _) implements JSObject {
+  external String get type;
+  external String get value;
 }
 
 extension type Argument._(JSObject _) implements JSObject {