How to remove an option from Firefox context menu

How to remove an option from Firefox context menu

1. Look up the CSS selector of the option:
   1. open developer tools ([F12] or options button (---) -> Web Developer -> Toggle Tools);
   2. open the settings ([F1] or options button (...) -> Settings);
   3. select checkbox "Enable browser chrome and add-on debugging toolboxes";
   4. select checkbox "Enable remote debugging";
   5. open browser debugging toolbox by pressing [Ctrl]+[Alt]+[Shift]+[I];
   6. confirm "Incoming Connection" by "OK";
   7. in the browser debugging toolbox, click on options button (...) -> Disable popup auto-hide (you can manually close the popups by pressing [Esc]);
   8. open a context menu the option appears in;
      for example, if you want to remove "Email Image...", right-click on some image on any web page;
   9. switch back to the browser debugging toolbox window;
      if it is not visible and cannot be switched to by using the mouse, use the appropriate key shortcuts, e.g., [Alt]+[Tab];
   10. look up the selector as with a web page – using "Inspect Element".
   
   The CSS selector for option "Email Image..." is:

   #context-sendimage

2. Add a CSS definition that hides the element:
   
   1. open "userChrome.css":
      1. options button (---) -> Help -> Troubleshooting Information -> Open Directory;
      2. create or open folder "chrome";
      3. create or open file "userChrome.css";
   2. add a CSS definition to the content of the file, that would hide "Email Image..." element:
      

      #context-sendimage {
          display: none;
      }

   changes take effect once you've saved the file and restarted the browser;
3. do not forget to reset the popup auto-hide option (and other settings that were changed).
4. if the customisations do not get applied and you're using Firefox ≥69, you need to enable the loading of "userChrome.css" (which is disabled by default because it supposedly slows down the startup of Firefox a bit):
   
   1. open address "about:config" (type it into the address bar and press [Enter]);
   2. click on "Accept the Risk and Continue";
   3. find option "toolkit.legacyUserProfileCustomizations.stylesheets" (paste its name into the filter bar);
   4. double-click on the option to switch it to "true";
   5. close the tab.

See also:

• https://support.mozilla.org/en-US/questions/1123903
• https://developer.mozilla.org/en-US/docs/Tools/Browser_Toolbox
• https://github.com/Aris-t2/CustomCSSforFx