diff --git a/Userland/Libraries/LibWeb/HTML/WindowOrWorkerGlobalScope.idl b/Userland/Libraries/LibWeb/HTML/WindowOrWorkerGlobalScope.idl
new file mode 100644
index 0000000000..82e66c92bf
--- /dev/null
+++ b/Userland/Libraries/LibWeb/HTML/WindowOrWorkerGlobalScope.idl
@@ -0,0 +1,28 @@
+// https://html.spec.whatwg.org/multipage/webappapis.html#windoworworkerglobalscope
+interface mixin WindowOrWorkerGlobalScope {
+    [Replaceable] readonly attribute USVString origin;
+    readonly attribute boolean isSecureContext;
+    readonly attribute boolean crossOriginIsolated;
+
+    // FIXME: undefined reportError(any e);
+
+    // base64 utility methods
+    DOMString btoa(DOMString data);
+    ByteString atob(DOMString data);
+
+    // timers
+    // FIXME: long setTimeout(TimerHandler handler, optional long timeout = 0, any... arguments);
+    // FIXME: undefined clearTimeout(optional long id = 0);
+    // FIXME: long setInterval(TimerHandler handler, optional long timeout = 0, any... arguments);
+    // FIXME: undefined clearInterval(optional long id = 0);
+
+    // microtask queuing
+    // FIXME: undefined queueMicrotask(VoidFunction callback);
+
+    // ImageBitmap
+    // FIXME: Promise<ImageBitmap> createImageBitmap(ImageBitmapSource image, optional ImageBitmapOptions options = {});
+    // FIXME: Promise<ImageBitmap> createImageBitmap(ImageBitmapSource image, long sx, long sy, long sw, long sh, optional ImageBitmapOptions options = {});
+
+    // structured cloning
+    // FIXME: any structuredClone(any value, optional StructuredSerializeOptions options = {});
+};
diff --git a/Userland/Libraries/LibWeb/HTML/WorkerGlobalScope.idl b/Userland/Libraries/LibWeb/HTML/WorkerGlobalScope.idl
index 136a48536f..a595badd04 100644
--- a/Userland/Libraries/LibWeb/HTML/WorkerGlobalScope.idl
+++ b/Userland/Libraries/LibWeb/HTML/WorkerGlobalScope.idl
@@ -1,8 +1,10 @@
 #import <DOM/EventTarget.idl>
 #import <DOM/EventHandler.idl>
+#import <HTML/WindowOrWorkerGlobalScope.idl>
 #import <HTML/WorkerLocation.idl>
 #import <HTML/WorkerNavigator.idl>
 
+// https://html.spec.whatwg.org/multipage/workers.html#workerglobalscope
 [Exposed=Worker]
 interface WorkerGlobalScope : EventTarget {
     readonly attribute WorkerGlobalScope self;
@@ -16,13 +18,6 @@ interface WorkerGlobalScope : EventTarget {
     attribute EventHandler ononline;
     attribute EventHandler onrejectionhandled;
     attribute EventHandler onunhandledrejection;
-
-    // FIXME: These should all come from a WindowOrWorkerGlobalScope mixin
-    [Replaceable] readonly attribute USVString origin;
-    readonly attribute boolean isSecureContext;
-    readonly attribute boolean crossOriginIsolated;
-
-    // base64 utility methods
-    DOMString btoa(DOMString data);
-    ByteString atob(DOMString data);
 };
+
+WorkerGlobalScope includes WindowOrWorkerGlobalScope;