diff --git a/Userland/Libraries/LibWeb/HTML/Window.cpp b/Userland/Libraries/LibWeb/HTML/Window.cpp
index db5ef88654d..3e62021000e 100644
--- a/Userland/Libraries/LibWeb/HTML/Window.cpp
+++ b/Userland/Libraries/LibWeb/HTML/Window.cpp
@@ -1063,7 +1063,6 @@ WebIDL::ExceptionOr<void> Window::initialize_web_interfaces(Badge<WindowEnvironm
     define_native_function(realm, "clearTimeout", clear_timeout, 1, attr);
     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, "focus", focus, 0, attr);
 
     define_native_function(realm, "queueMicrotask", queue_microtask, 1, attr);
@@ -1472,35 +1471,6 @@ JS_DEFINE_NATIVE_FUNCTION(Window::cancel_idle_callback)
     return JS::js_undefined();
 }
 
-// https://html.spec.whatwg.org/multipage/webappapis.html#dom-atob-dev
-JS_DEFINE_NATIVE_FUNCTION(Window::atob)
-{
-    if (!vm.argument_count())
-        return vm.throw_completion<JS::TypeError>(JS::ErrorType::BadArgCountOne, "atob");
-    auto deprecated_string = TRY(vm.argument(0).to_deprecated_string(vm));
-    auto string = String::from_utf8(deprecated_string).release_value_but_fixme_should_propagate_errors();
-
-    // must throw an "InvalidCharacterError" DOMException if data contains any character whose code point is greater than U+00FF
-    for (auto code_point : string.code_points()) {
-        if (code_point > 0x00FF)
-            return throw_completion(WebIDL::InvalidCharacterError::create(*vm.current_realm(), "Data contains characters outside the range U+0000 and U+00FF"));
-    }
-
-    // Otherwise, the user agent must convert data to a byte sequence whose nth byte is the eight-bit representation of the nth code point of data
-    // and then must apply forgiving-base64 encode to that byte sequence and return the result.
-    auto decoded = Infra::decode_forgiving_base64(StringView(deprecated_string));
-    if (decoded.is_error())
-        return vm.throw_completion<JS::TypeError>(JS::ErrorType::InvalidFormat, "Base64");
-
-    // The bytes object might contain bytes greater than 128, encode them in UTF8
-    // NOTE: Any 8-bit encoding -> utf-8 decoder will work for this
-    auto text_decoder = TextCodec::decoder_for("windows-1252"sv);
-    VERIFY(text_decoder.has_value());
-    auto text = TRY_OR_THROW_OOM(vm, text_decoder->to_utf8(decoded.release_value()));
-
-    return JS::PrimitiveString::create(vm, text);
-}
-
 // 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 2bb6dfc368b..4cbd88ac51d 100644
--- a/Userland/Libraries/LibWeb/HTML/Window.h
+++ b/Userland/Libraries/LibWeb/HTML/Window.h
@@ -46,6 +46,7 @@ public:
 
     ~Window();
 
+    using WindowOrWorkerGlobalScopeMixin::atob;
     using WindowOrWorkerGlobalScopeMixin::btoa;
 
     // ^DOM::EventTarget
@@ -266,7 +267,6 @@ private:
     JS_DECLARE_NATIVE_FUNCTION(clear_timeout);
     JS_DECLARE_NATIVE_FUNCTION(request_animation_frame);
     JS_DECLARE_NATIVE_FUNCTION(cancel_animation_frame);
-    JS_DECLARE_NATIVE_FUNCTION(atob);
     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 029f3f7ff3d..1ca2aa2c523 100644
--- a/Userland/Libraries/LibWeb/HTML/Window.idl
+++ b/Userland/Libraries/LibWeb/HTML/Window.idl
@@ -40,6 +40,7 @@ interface Window : EventTarget {
     [Replaceable] readonly attribute USVString origin;
     readonly attribute boolean isSecureContext;
     DOMString btoa(DOMString data);
+    ByteString atob(DOMString data);
 };
 Window includes GlobalEventHandlers;
 Window includes WindowEventHandlers;