Hi khaled, Firefox doesn't have a built-in menu editor, and extensions are not empowered to change built-in menus. That only leaves one mechanism to hide menu items, which is the optional userChrome.css file method.

When you have 10 minutes to spare, this is how you set it up:

This assumes you do not already have a userChrome.css file. If you do already have a working userChrome.css file, you just need to add the rule under (A) to your file.

(A) Select and copy the following style rule code

/* Hide "Select All Tabs" on context menu */
#context_selectAllTabs {
  display: none !important;
}

(B) Generate and download a userChrome.css file

Open the following page and paste the above rules into the editor, replacing the sample rule:

https://www.userchrome.org/download-userchrome-css.html

Then click "Generate CSS File" and save the userChrome.css file to your computer. (See first attached screenshot)

Use the downloads list on the toolbar to open the downloads folder directly to the new userChrome.css file. (See second attached screenshot)

Minimize that Windows Explorer window for later reference.

(C) Create a new chrome folder in your profile folder

The following article has the detailed steps for that (#1, #2, and I recommend #3)

https://www.userchrome.org/how-create-userchrome-css.html

There are boring videos for Windows and Mac if you like videos.

(D) Move the userChrome.css file you generated in Step B into the chrome folder you created in Step C

The next time you exit Firefox and start it up again, it should discover that file and apply the rule.

Firefox 69+ users: If you didn't set up your userChrome.css file in Firefox 68 or earlier, there's an extra step:

(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button promising to be careful or accepting the risk.

(2) In the search box above the list, type or paste cust and pause while the list is filtered

(3) Double-click the toolkit.legacyUserProfileCustomizations.stylesheets preference to switch the value from false to true

Note that the items in the Tab bar context menu get a 's' appended (i.e. Tabs instead of Tab) and that 'Select All Tabs' is grayed in this case.

You can add code to the userChrome.css file below the default @namespace line.

• http://kb.mozillazine.org/userChrome.css

@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"); /* only needed once */

#context_selectAllTabs { display:none!important; }

It is not that difficult to create userChrome.css if you have never used it.

The first step is to open the "Help -> Troubleshooting Information" page and find the button to access the profile folder.

• https://support.mozilla.org/en-US/kb/use-troubleshooting-information-page-fix-firefox

You can find this button under the "Application Basics" section as "Profile Folder -> Open Folder". If you click this button then you open the profile folder in the Windows File Explorer. You need to create a folder with the name chrome in this folder (name is all lowercase). In the chrome folder you need to create a plian text file with the name userChrome.css (name is case sensitive). In this userChrome.css text file you paste the text posted.

You need to close (Quit/Exit) and restart Firefox when you create or modify the userChrome.css file.

See also:

• https://www.userchrome.org/how-create-userchrome-css.html

thank you a lot folks