diff --git a/mw/confirmCloseWindow.d.ts b/mw/confirmCloseWindow.d.ts
new file mode 100644
index 0000000..0378fda
--- /dev/null
+++ b/mw/confirmCloseWindow.d.ts
@@ -0,0 +1,69 @@
+interface Options {
+    /**
+     * Optional jQuery event namespace, to allow loosely coupled
+     * external code to release your trigger. For example, the VisualEditor extension can use this
+     * remove the trigger registered by mediawiki.action.edit, without strong runtime coupling.
+     */
+    namespace?: string;
+
+    /**
+     * @returns {boolean} Whether to show the dialog to the user.
+     */
+    test?(): boolean;
+}
+
+interface ConfirmCloseWindow {
+    /**
+     * Remove the event listener and don't show an alert anymore, if the user wants to leave
+     * the page.
+     */
+    release(): void;
+
+    /**
+     * Trigger the module's function manually.
+     *
+     * Check, if options.test() returns true and show an alert to the user if he/she want
+     * to leave this page. Returns false, if options.test() returns false or the user
+     * cancelled the alert window (~don't leave the page), true otherwise.
+     *
+     * @returns {boolean}
+     */
+    trigger(): boolean;
+}
+
+declare global {
+    namespace mw {
+        /**
+         * Prevent the closing of a window with a confirm message (the onbeforeunload event seems to
+         * work in most browsers.)
+         *
+         * This supersedes any previous onbeforeunload handler. If there was a handler before, it is
+         * restored when you execute the returned release() function.
+         *
+         * ```js
+         * var allowCloseWindow = mw.confirmCloseWindow();
+         * // ... do stuff that can't be interrupted ...
+         * allowCloseWindow.release();
+         * ```
+         *
+         * The second function returned is a trigger function to trigger the check and an alert
+         * window manually, e.g.:
+         *
+         * ```js
+         * var allowCloseWindow = mw.confirmCloseWindow();
+         * // ... do stuff that can't be interrupted ...
+         * if ( allowCloseWindow.trigger() ) {
+         *     // don't do anything (e.g. destroy the input field)
+         * } else {
+         *     // do whatever you wanted to do
+         * }
+         * ```
+         *
+         * @param {Options} [options]
+         * @returns {ConfirmCloseWindow} An object of functions to work with this module
+         */
+        function confirmCloseWindow(options?: Options): ConfirmCloseWindow;
+    }
+}
+
+export {};
diff --git a/mw/index.d.ts b/mw/index.d.ts
index ffe3d7d..f5534da 100644
--- a/mw/index.d.ts
+++ b/mw/index.d.ts
@@ -1,5 +1,6 @@
 import "./Api";
 import "./config";
+import "./confirmCloseWindow";
 import "./cookie";
 import "./ForeignApi";
 import "./ForeignRest";