Firefox tweak: more compact tabs

  1. Open a new tab on about:support
  2. Click the button next to “Profile Folder”
  3. Go to the “chrome” directory at the profile folder, or create it if it doesn’t exist.
  4. Create a file named “userChrome.css” (if it doesn’t exist) and open it in a text editor.
  5. Copy the css code from github.com/andreicristianpetcu/UserChrome-Tweaks
    (copy of the css is at the bottom of this post)
  6. Paste it into userChrome.css and save.
  7. Restart Firefox

userChrome.css

/* 
* Makes tabs only 22px high rather than the default 29px
* Only works on compact mode, otherwise tab height will be normal
*/

[uidensity="compact"]:root {
  --tab-min-height: 22px !important;
  --newtab-margin: -3px 0 -3px -3px !important;
}

.tabbrowser-tab {
  max-height: var(--tab-min-height) !important;
}

.tabs-newtab-button{
  margin: var(--newtab-margin) !important;
}