diff --git a/Userland/Libraries/LibWeb/HTML/Window.cpp b/Userland/Libraries/LibWeb/HTML/Window.cpp
index f00e6bbf8f..6110804e6d 100644
--- a/Userland/Libraries/LibWeb/HTML/Window.cpp
+++ b/Userland/Libraries/LibWeb/HTML/Window.cpp
@@ -750,24 +750,6 @@ float Window::device_pixel_ratio() const
     return 1.0f;
 }
 
-// https://drafts.csswg.org/cssom-view/#dom-window-outerwidth
-int Window::outer_width() const
-{
-    // The outerWidth attribute must return the width of the client window. If there is no client window this attribute must return zero.
-    if (auto* page = this->page())
-        return page->window_size().width().value();
-    return 0;
-}
-
-// https://drafts.csswg.org/cssom-view/#dom-window-screeny
-int Window::outer_height() const
-{
-    // The outerHeight attribute must return the height of the client window. If there is no client window this attribute must return zero.
-    if (auto* page = this->page())
-        return page->window_size().height().value();
-    return 0;
-}
-
 // https://html.spec.whatwg.org/multipage/webstorage.html#dom-localstorage
 JS::NonnullGCPtr<HTML::Storage> Window::local_storage()
 {
@@ -996,10 +978,6 @@ WebIDL::ExceptionOr<void> Window::initialize_web_interfaces(Badge<WindowEnvironm
 
     define_native_function(realm, "fetch", Bindings::fetch, 1, attr);
 
-    // FIXME: These properties should be [Replaceable] according to the spec, but [Writable+Configurable] is the closest we have.
-    define_native_accessor(realm, "outerWidth", outer_width_getter, {}, attr);
-    define_native_accessor(realm, "outerHeight", outer_height_getter, {}, attr);
-
     define_direct_property("CSS", MUST_OR_THROW_OOM(heap().allocate<Bindings::CSSNamespace>(realm, realm)), 0);
 
     define_native_accessor(realm, "localStorage", local_storage_getter, {}, attr);
@@ -1455,6 +1433,26 @@ i32 Window::screen_y() const
     return 0;
 }
 
+// https://w3c.github.io/csswg-drafts/cssom-view/#dom-window-outerwidth
+i32 Window::outer_width() const
+{
+    // The outerWidth attribute must return the width of the client window. If there is no client window this
+    // attribute must return zero.
+    if (auto* page = this->page())
+        return page->window_size().width().value();
+    return 0;
+}
+
+// https://w3c.github.io/csswg-drafts/cssom-view/#dom-window-outerheight
+i32 Window::outer_height() const
+{
+    // The outerHeight attribute must return the height of the client window. If there is no client window this
+    // attribute must return zero.
+    if (auto* page = this->page())
+        return page->window_size().height().value();
+    return 0;
+}
+
 // https://w3c.github.io/hr-time/#dom-windoworworkerglobalscope-performance
 WebIDL::ExceptionOr<JS::NonnullGCPtr<HighResolutionTime::Performance>> Window::performance()
 {
@@ -1675,18 +1673,6 @@ JS_DEFINE_NATIVE_FUNCTION(Window::get_selection)
     return impl->associated_document().get_selection();
 }
 
-JS_DEFINE_NATIVE_FUNCTION(Window::outer_width_getter)
-{
-    auto* impl = TRY(impl_from(vm));
-    return JS::Value(impl->outer_width());
-}
-
-JS_DEFINE_NATIVE_FUNCTION(Window::outer_height_getter)
-{
-    auto* impl = TRY(impl_from(vm));
-    return JS::Value(impl->outer_height());
-}
-
 JS_DEFINE_NATIVE_FUNCTION(Window::structured_clone)
 {
     auto* impl = TRY(impl_from(vm));
diff --git a/Userland/Libraries/LibWeb/HTML/Window.h b/Userland/Libraries/LibWeb/HTML/Window.h
index 390d3facc6..9dac88f53b 100644
--- a/Userland/Libraries/LibWeb/HTML/Window.h
+++ b/Userland/Libraries/LibWeb/HTML/Window.h
@@ -115,9 +115,6 @@ public:
 
     float device_pixel_ratio() const;
 
-    int outer_width() const;
-    int outer_height() const;
-
     JS::NonnullGCPtr<HTML::Storage> local_storage();
     JS::NonnullGCPtr<HTML::Storage> session_storage();
 
@@ -179,6 +176,8 @@ public:
 
     i32 screen_x() const;
     i32 screen_y() const;
+    i32 outer_width() const;
+    i32 outer_height() const;
 
     WebIDL::ExceptionOr<JS::NonnullGCPtr<HighResolutionTime::Performance>> performance();
 
@@ -248,9 +247,6 @@ private:
 
     JS_DECLARE_NATIVE_FUNCTION(device_pixel_ratio_getter);
 
-    JS_DECLARE_NATIVE_FUNCTION(outer_width_getter);
-    JS_DECLARE_NATIVE_FUNCTION(outer_height_getter);
-
     JS_DECLARE_NATIVE_FUNCTION(structured_clone);
 
     JS_DECLARE_NATIVE_FUNCTION(local_storage_getter);
diff --git a/Userland/Libraries/LibWeb/HTML/Window.idl b/Userland/Libraries/LibWeb/HTML/Window.idl
index 2a9d648f6a..a882f3fc05 100644
--- a/Userland/Libraries/LibWeb/HTML/Window.idl
+++ b/Userland/Libraries/LibWeb/HTML/Window.idl
@@ -69,6 +69,8 @@ interface Window : EventTarget {
     [Replaceable, ImplementedAs=screen_x] readonly attribute long screenLeft;
     [Replaceable] readonly attribute long screenY;
     [Replaceable, ImplementedAs=screen_y] readonly attribute long screenTop;
+    [Replaceable] readonly attribute long outerWidth;
+    [Replaceable] readonly attribute long outerHeight;
 
     // FIXME: Everything from here on should be shared through WindowOrWorkerGlobalScope
     // https://w3c.github.io/hr-time/#the-performance-attribute