I have Firefox Quantum web-browser version 57.0.2 (64-bit) in Windows 7.

The Sidebar, unfortunately, has a maximum width of about 540 pixels.

I tried to increase this constraint by going to about:config and searching for "sidebar". Then I changed the setting devtools.toolbox.sidebar.width;500 to a value of 600. Then I restarted Firefox. But it did not work.

So how can I increase the maximum width of the sidebar?

2 Answers 2

  1. Firefox menu -> Help -> Troubleshooting Information -> Profile folder -> Open folder

  2. There should be folder named chrome (all lowercased). If it's missing, create it.

  3. In said chrome folder, there's userChrome.css file. If it does not exist, create it.

  4. Open this file with any text editor.

  5. In this file, if there is no CSS rule #sidebar, create it:

/* remove maximum/minimum width restriction of sidebar */
#sidebar {
  max-width: none !important;
  min-width: 0px !important;
  1. Restart Firefox
  • Confirmed in FF 66: No config settings work, but this method does. No way to improve it.
    – u2n
    May 2, 2019 at 19:16
  • Did not work on FF 70.0.1.
    – wha7ever
    Nov 12, 2019 at 15:46
  • 6
    Since version 69 and later, Firefox does not load userChrome.css by default. To make it effective again, open about:config in Firefox and set the preference toolkit.legacyUserProfileCustomizations.stylesheets to true
    – mini
    Nov 29, 2019 at 8:42
  • Does not seem to work on FF 71. Dec 18, 2019 at 12:28
  • 1
    How do you guys know all of this stuff wth?
    – 55 Cancri
    Jun 28, 2020 at 13:49

reload the browser

  • How is this better than accepted answer?
    – Toto
    Jul 2 at 15:49
  • there have been changes in how to locate the profile folder for some firefox versions Jul 27 at 22:52

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.