diff --git a/Userland/Libraries/LibWeb/HTML/Window.cpp b/Userland/Libraries/LibWeb/HTML/Window.cpp
index 30d40feaee..db5ef88654 100644
--- a/Userland/Libraries/LibWeb/HTML/Window.cpp
+++ b/Userland/Libraries/LibWeb/HTML/Window.cpp
@@ -1064,7 +1064,6 @@ WebIDL::ExceptionOr<void> Window::initialize_web_interfaces(Badge<WindowEnvironm
     define_native_function(realm, "requestAnimationFrame", request_animation_frame, 1, attr);
     define_native_function(realm, "cancelAnimationFrame", cancel_animation_frame, 1, attr);
     define_native_function(realm, "atob", atob, 1, attr);
-    define_native_function(realm, "btoa", btoa, 1, attr);
     define_native_function(realm, "focus", focus, 0, attr);
 
     define_native_function(realm, "queueMicrotask", queue_microtask, 1, attr);
@@ -1502,24 +1501,6 @@ JS_DEFINE_NATIVE_FUNCTION(Window::atob)
     return JS::PrimitiveString::create(vm, text);
 }
 
-JS_DEFINE_NATIVE_FUNCTION(Window::btoa)
-{
-    if (!vm.argument_count())
-        return vm.throw_completion<JS::TypeError>(JS::ErrorType::BadArgCountOne, "btoa");
-    auto string = TRY(vm.argument(0).to_deprecated_string(vm));
-
-    Vector<u8> byte_string;
-    byte_string.ensure_capacity(string.length());
-    for (u32 code_point : Utf8View(string)) {
-        if (code_point > 0xff)
-            return throw_completion(WebIDL::InvalidCharacterError::create(*vm.current_realm(), "Data contains characters outside the range U+0000 and U+00FF"));
-        byte_string.append(code_point);
-    }
-
-    auto encoded = MUST(encode_base64(byte_string.span()));
-    return JS::PrimitiveString::create(vm, encoded.to_deprecated_string());
-}
-
 // https://html.spec.whatwg.org/multipage/interaction.html#dom-window-focus
 JS_DEFINE_NATIVE_FUNCTION(Window::focus)
 {
diff --git a/Userland/Libraries/LibWeb/HTML/Window.h b/Userland/Libraries/LibWeb/HTML/Window.h
index 440311b930..2bb6dfc368 100644
--- a/Userland/Libraries/LibWeb/HTML/Window.h
+++ b/Userland/Libraries/LibWeb/HTML/Window.h
@@ -46,6 +46,8 @@ public:
 
     ~Window();
 
+    using WindowOrWorkerGlobalScopeMixin::btoa;
+
     // ^DOM::EventTarget
     virtual bool dispatch_event(DOM::Event&) override;
 
@@ -265,7 +267,6 @@ private:
     JS_DECLARE_NATIVE_FUNCTION(request_animation_frame);
     JS_DECLARE_NATIVE_FUNCTION(cancel_animation_frame);
     JS_DECLARE_NATIVE_FUNCTION(atob);
-    JS_DECLARE_NATIVE_FUNCTION(btoa);
     JS_DECLARE_NATIVE_FUNCTION(focus);
 
     JS_DECLARE_NATIVE_FUNCTION(get_computed_style);
diff --git a/Userland/Libraries/LibWeb/HTML/Window.idl b/Userland/Libraries/LibWeb/HTML/Window.idl
index 7702f5e363..029f3f7ff3 100644
--- a/Userland/Libraries/LibWeb/HTML/Window.idl
+++ b/Userland/Libraries/LibWeb/HTML/Window.idl
@@ -39,6 +39,7 @@ interface Window : EventTarget {
     // FIXME: Replace these with 'Window includes WindowOrWorkerGlobalScope;' once we have feature parity
     [Replaceable] readonly attribute USVString origin;
     readonly attribute boolean isSecureContext;
+    DOMString btoa(DOMString data);
 };
 Window includes GlobalEventHandlers;
 Window includes WindowEventHandlers;