diff --git a/gluon.d.ts b/gluon.d.ts
index 260ae62..9d8fad7 100644
--- a/gluon.d.ts
+++ b/gluon.d.ts
@@ -339,7 +339,10 @@ type Window = {
   controls: ControlsApi,
 
   /** Close the Gluon window. */
-  close(): void
+  close(): void,
+
+  /** If the window has been closed or not. */
+  closed: Boolean
 };
 
 
diff --git a/src/launcher/inject.js b/src/launcher/inject.js
index 4a01d15..a3717b3 100644
--- a/src/launcher/inject.js
+++ b/src/launcher/inject.js
@@ -134,12 +134,17 @@ export default async (CDP, proc, injectionType = 'browser', { dataPath, browserN
     },
 
     close: () => {
+      if (Window.closed) return false;
+
       for (const handler of closeHandlers) handler(); // extra api handlers which need to be closed
 
       CDP.sendMessage('Browser.close');
       CDP.close();
       proc.kill();
+
+      return Window.closed = true;
     },
+    closed: false,
 
     versions
   };