feat: add option to disable Ctrl+W close shortcut

browser/base/content/browser.js

@@ -1377,6 +1377,13 @@ var gLastOpenDirectory = {
         this._lastDir
       );
     }
+
+    if (BrowserUIUtils.closeShortcutDisabled) {
+      document.getElementById("key_close").remove();
+      document.getElementById("menu_close").removeAttribute("key");
+      document.getElementById("key_closeWindow").remove();
+      document.getElementById("menu_closeWindow").removeAttribute("key");
+    }
   },
   reset() {
     this._lastDir = null;

browser/base/content/nonbrowser-mac.js

@@ -110,6 +110,12 @@ var NonBrowserWindow = {
         document.getElementById("key_quitApplication").remove();
         document.getElementById("menu_FileQuitItem").removeAttribute("key");
       }
+      if (BrowserUIUtils.closeShortcutDisabled) {
+        document.getElementById("key_close").remove();
+        document.getElementById("menu_close").removeAttribute("key");
+        document.getElementById("key_closeWindow").remove();
+        document.getElementById("menu_closeWindow").removeAttribute("key");
+      }
     }
 
     this.delayedStartupTimeoutId = setTimeout(() => this.delayedStartup(), 0);

browser/components/tests/browser/browser_close_disabled.js

@@ -0,0 +1,62 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+add_task(async function test_appMenu_close_disabled() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["browser.closeShortcut.disabled", true]],
+  });
+
+  let win = await BrowserTestUtils.openNewBrowserWindow();
+  let doc = win.document;
+
+  let menuButton = doc.getElementById("PanelUI-menu-button");
+  menuButton.click();
+  await BrowserTestUtils.waitForEvent(win.PanelUI.mainView, "ViewShown");
+
+  let closeButton = doc.querySelector(`[key="key_closeWindow"]`);
+  is(closeButton, null, "No close button with shortcut key");
+
+  await BrowserTestUtils.closeWindow(win);
+
+  await SpecialPowers.popPrefEnv();
+});
+
+add_task(async function test_close_shortcut_disabled() {
+  async function testCloseShortcut(shouldClose) {
+    let win = await BrowserTestUtils.openNewBrowserWindow();
+
+    let closeRequested = false;
+    let observer = {
+      observe(subject, topic, data) {
+        is(topic, "close-application-requested", "Right observer topic");
+        ok(shouldClose, "Close shortcut should NOT have worked");
+
+        // Don't actually close the browser when testing.
+        let cancelClose = subject.QueryInterface(Ci.nsISupportsPRBool);
+        cancelClose.data = true;
+
+        closeRequested = true;
+      },
+    };
+    Services.obs.addObserver(observer, "close-application-requested");
+
+    let modifiers = { accelKey: true };
+    if (AppConstants.platform == "win") {
+      modifiers.shiftKey = true;
+    }
+    EventUtils.synthesizeKey("w", modifiers, win);
+
+    await BrowserTestUtils.closeWindow(win);
+    Services.obs.removeObserver(observer, "close-application-requested");
+
+    is(closeRequested, shouldClose, "Expected close state");
+  }
+
+  // Close shortcut should work when pref is not set.
+  await testCloseShortcut(true);
+
+  await SpecialPowers.pushPrefEnv({
+    set: [["browser.closeShortcut.disabled", true]],
+  });
+  await testCloseShortcut(false);
+});

browser/modules/BrowserUIUtils.sys.mjs

@@ -174,3 +174,10 @@ XPCOMUtils.defineLazyPreferenceGetter(
   "browser.quitShortcut.disabled",
   false
 );
+
+XPCOMUtils.defineLazyPreferenceGetter(
+  BrowserUIUtils,
+  "closeShortcutDisabled",
+  "browser.closeShortcut.disabled",
+  false
+);

waterfox/browser/app/profile/03-features.js

@@ -214,6 +214,9 @@ pref("browser.ml.chat.enabled", false); // Disable built-in ML chat features.
 // Image Format Support
 pref("image.jxl.enabled", true); // Enable support for the JPEG XL image format.
 
+// Keyboard Shortcuts
+pref("browser.closeShortcut.disabled", false); // false = Ctrl+W (or Cmd+W) closes tab/window (default behavior). true = disables this shortcut.
+
 // Restart Menu (often provided by extensions or custom builds, not a standard Firefox feature)
 pref("browser.restart_menu.showpanelmenubtn", true); // If a restart menu is present, show its button in a panel menu.
 pref("browser.restart_menu.purgecache", false); // If true, purges caches upon restart initiated via this menu.