Only closing a window (Ctrl+Shift+W) could possibly make Firefox display a warning, closing a tab is always done without a warning as you can reopen a closed tab via Ctrl+Shift+T.

You can possibly disable the key_close (Ctrl+W) and possibly also key_closeWindow (Ctrl+Shift+W) via an autoconfig.cfg file.

• https://support.mozilla.org/en-US/kb/customizing-firefox-using-autoconfig

See:

• /questions/1367908 How to allow web page to override a keyboard shortcut

I'm not a js developer could you bear my nobleness? Because created these files but I think skipping something...

According to the this guide,I created two file ones named "autoconfig.js" under /usr/lib/firefox/defaults/pref

The content of the autoconfig.js is:

pref("general.config.filename", "firefox.cfg");                                 
pref("general.config.obscure_value", 0)                                         
                                                                                 
pref("key_close", 0)                                                            
pref("key_closeWindow", 0)                                                      
                                                                                 
unlockPref("pref.general.key_close")                                            
unlockPref("pref.general.key_closeWindow")  

Also provided EL with vim :set ff=unix

another is named firefox.cfg under /usr/lib/firefox/ then content

cat firefox.cfg // IMPORTANT: Start your code on the 2nd line

Also provided EL with vim :set ff=unix for so it's not working.

You can use the autoconfig.cfg file in the Firefox installation folder to initialize (set/lock) preferences and run privileged JavaScript code.

To use Autoconfig, place two files into the Firefox installation directory.

• on Windows and Linux, they go into the same directory where Firefox is installed
• on macOS, they go into the Contents/Resources directory of the Firefox.app

The autoconfig.js file that specifies to use autoconfig.cfg is placed into the "defaults\pref" directory where the channel-prefs.js file is located. The autoconfig.cfg file is placed at the top level of the Firefox directory.

• autoconfig.cfg and autoconfig.js need to start with a comment line (//)
• autoconfig.js needs to use Unix line endings (LF instead of CR/LF)

See also:

• https://support.mozilla.org/en-US/kb/customizing-firefox-using-autoconfig

The content of autoconfig.js:

//
pref("general.config.filename", "autoconfig.cfg");
pref("general.config.obscure_value", 0);
pref("general.config.sandbox_enabled", false);

The content of autoconfig.cfg:

let { classes: Cc, interfaces: Ci, manager: Cm  } = Components;
let Services = globalThis.Services || ChromeUtils.import("resource://gre/modules/Services.jsm").Services;
function ConfigJS() { Services.obs.addObserver(this, 'chrome-document-global-created', false); }
ConfigJS.prototype = {
  observe: function (aSubject) { aSubject.addEventListener('DOMContentLoaded', this, {once: true}); },
  handleEvent: function (aEvent) {
    let document = aEvent.originalTarget;
    let window = document.defaultView;
    let location = window.location;
    if (/^(chrome:(?!\/\/(global\/content\/commonDialog|browser\/content\/webext-panels)\.x?html)|about:(?!blank))/i.test(location.href)) {
      if (window._gBrowser) {
        let keys = ["key_close","key_closeWindow"];
        for (var i=0; i < keys.length; i++) {
          let keyCommand = window.document.getElementById(keys[i]);
          if (keyCommand != undefined) { 
            keyCommand.removeAttribute("command"); 
            keyCommand.removeAttribute("key"); 
            keyCommand.removeAttribute("modifiers"); 
            keyCommand.removeAttribute("oncommand"); 
            keyCommand.removeAttribute("data-l10n-id"); 
          }
        }
      }
    }
  }
};
if (!Services.appinfo.inSafeMode) { new ConfigJS(); }

You can use the autoconfig.cfg file in the Firefox installation folder to initialize (set/lock) preferences and run privileged JavaScript code. To use Autoconfig, place two files into the Firefox installation directory.

• on Windows and Linux, they go into the same directory where Firefox is installed
• on macOS, they go into the Contents/Resources directory of the Firefox.app

The autoconfig.js file that specifies to use autoconfig.cfg is placed into the "defaults\pref" directory where the channel-prefs.js file is located. The autoconfig.cfg file is placed at the top level of the Firefox directory.

• autoconfig.cfg and autoconfig.js need to start with a comment line (//)
• autoconfig.js needs to use Unix line endings (LF instead of CR/LF)

See also:

• https://support.mozilla.org/en-US/kb/customizing-firefox-using-autoconfig

---

The content of autoconfig.js:

//
pref("general.config.filename", "autoconfig.cfg");
pref("general.config.obscure_value", 0);
pref("general.config.sandbox_enabled", false);

The content of autoconfig.cfg:

let { classes: Cc, interfaces: Ci, manager: Cm  } = Components;
const {Services} = Components.utils.import('resource://gre/modules/Services.jsm');
function ConfigJS() { Services.obs.addObserver(this, 'chrome-document-global-created', false); }
ConfigJS.prototype = {
  observe: function (aSubject) { aSubject.addEventListener('DOMContentLoaded', this, {once: true}); },
  handleEvent: function (aEvent) {
    let document = aEvent.originalTarget;
    let window = document.defaultView;
    let location = window.location;
    if (/^(chrome:(?!\/\/(global\/content\/commonDialog|browser\/content\/webext-panels)\.x?html)|about:(?!blank))/i.test(location.href)) {
      if (window._gBrowser) {
        let keys = ["key_close","key_closeWindow"];
        for (var i=0; i < keys.length; i++) {
          let keyCommand = window.document.getElementById(keys[i]);
          if (keyCommand != undefined) { 
            keyCommand.removeAttribute("command"); 
            keyCommand.removeAttribute("key"); 
            keyCommand.removeAttribute("modifiers"); 
            keyCommand.removeAttribute("oncommand"); 
            keyCommand.removeAttribute("data-l10n-id"); 
          }
        }
      }
    }
  }
};
if (!Services.appinfo.inSafeMode) { new ConfigJS(); }

thank you very much for this, unfortunately unlike the OP I am looking for something entirely different.

jumping to tabs 1-9 with Ctrl + 1 through 9, how do I disable them? in his case, closing tab term is "key_close" but I am not sure the term for Ctrl + 1-9. Also, how can I go about adding "Ctrl + `" to previous tab rather than Ctrl + Shift + Tab?

please help, thank you.

Hi wtfiwinomgs

That is about the key_selectTab (1-8) IDs and key_selectLastTab (9).

Hi wtfiwinomgs That is about the key_selectTab (1-8) IDs and key_selectLastTab (9).

oh thank you. I did find the xhtml but it looked very confusing.

what about binding a new key to previous tab? as well as binding new key to undo previously closed tab?

in the script is to disable key but how do I bind them?