diff --git a/components/script/dom/webidls/Window.webidl b/components/script/dom/webidls/Window.webidl
index 548821ac971..3c962f2795e 100644
--- a/components/script/dom/webidls/Window.webidl
+++ b/components/script/dom/webidls/Window.webidl
@@ -23,7 +23,7 @@
   //[Replaceable] readonly attribute BarProp toolbar;
   attribute DOMString status;
   void close();
-  //readonly attribute boolean closed;
+  readonly attribute boolean closed;
   //void stop();
   //void focus();
   //void blur();
diff --git a/components/script/dom/window.rs b/components/script/dom/window.rs
index 7d25b985c2c..b4459bf15db 100644
--- a/components/script/dom/window.rs
+++ b/components/script/dom/window.rs
@@ -509,6 +509,13 @@ impl WindowMethods for Window {
         }
     }
 
+    // https://html.spec.whatwg.org/multipage/#dom-window-closed
+    fn Closed(&self) -> bool {
+        self.window_proxy.get()
+            .map(|ref proxy| proxy.is_browsing_context_discarded())
+            .unwrap_or(true)
+    }
+
     // https://html.spec.whatwg.org/multipage/#dom-window-close
     fn Close(&self) {
         self.main_thread_script_chan()
diff --git a/tests/wpt/metadata/html/browsers/the-window-object/security-window/window-security.html.ini b/tests/wpt/metadata/html/browsers/the-window-object/security-window/window-security.html.ini
index 4fc54b9edaa..746b6a1c9c8 100644
--- a/tests/wpt/metadata/html/browsers/the-window-object/security-window/window-security.html.ini
+++ b/tests/wpt/metadata/html/browsers/the-window-object/security-window/window-security.html.ini
@@ -339,9 +339,6 @@
   [A SecurityError exception must be thrown when window.stop is accessed from a different origin.]
     expected: FAIL
 
-  [A SecurityError exception should not be thrown when window.closed is accessed from a different origin.]
-    expected: FAIL
-
   [A SecurityError exception should not be thrown when window.length is accessed from a different origin.]
     expected: FAIL
 
diff --git a/tests/wpt/metadata/html/dom/interfaces.html.ini b/tests/wpt/metadata/html/dom/interfaces.html.ini
index 2058e5125dc..dc075e84954 100644
--- a/tests/wpt/metadata/html/dom/interfaces.html.ini
+++ b/tests/wpt/metadata/html/dom/interfaces.html.ini
@@ -4341,9 +4341,6 @@
   [Window interface: attribute toolbar]
     expected: FAIL
 
-  [Window interface: attribute closed]
-    expected: FAIL
-
   [Window interface: operation stop()]
     expected: FAIL
 
@@ -4422,9 +4419,6 @@
   [Window interface: window must inherit property "toolbar" with the proper type (11)]
     expected: FAIL
 
-  [Window interface: window must inherit property "closed" with the proper type (14)]
-    expected: FAIL
-
   [Window interface: window must inherit property "stop" with the proper type (15)]
     expected: FAIL
 
diff --git a/tests/wpt/mozilla/meta/MANIFEST.json b/tests/wpt/mozilla/meta/MANIFEST.json
index 6e1e2c6fd99..ce6f56d9361 100644
--- a/tests/wpt/mozilla/meta/MANIFEST.json
+++ b/tests/wpt/mozilla/meta/MANIFEST.json
@@ -31734,7 +31734,7 @@
    "testharness"
   ],
   "mozilla/window.html": [
-   "8cfb22096cf713709d6206945ad1bb98a52c4136",
+   "455b488925ce1798c89c2944d4f13dee0cfa32b1",
    "testharness"
   ],
   "mozilla/window_performance.html": [
diff --git a/tests/wpt/mozilla/tests/mozilla/window.html b/tests/wpt/mozilla/tests/mozilla/window.html
index 1bc363a1122..b6dde8c6b8a 100644
--- a/tests/wpt/mozilla/tests/mozilla/window.html
+++ b/tests/wpt/mozilla/tests/mozilla/window.html
@@ -9,6 +9,7 @@
 test(function() {
   assert_equals(window, window.self);
   assert_true(window.self instanceof Window, "Should be Window");
+  assert_true(window.closed === false);
 });
 </script>
 </body>