I recently upgraded from firefox 55 to firefox 58 nightly and many extensions have to be updated. Treestyletabs is the only extension that I really use and it has been reimplemented as a sidebar panel. The difference is that it now has a giant bar at the top like this:

saying in really big letters Tree Style Tab. I was able to eliminate the tabs at the top of the screen by adding

#tabbrowser-tabs { visibility: collapse !important; }

to my .mozilla/firefox/???/chrome/userChrome.css file. I want to know if there is something similiar I can do to hide the sidebar panel header while still keeping the sidebar panel.

3 Answers 3


mannigfaltig said:

I've added a modification that removes any margin at the top:

#TabsToolbar, #sidebar-header {
  visibility: collapse !important;

#TabsToolbar {
  margin-bottom: -21px !important;

Then go to the hamburger menu > Customization and check "Title Bar" at the bottom left. Then it pretty much looks like FF 56.

I've also changed the style of TSTs in the add-on settings (all the way at the bottom; not in userChrome.css) such that the tabs don't take up as much vertical space and to hide the close box button (and only show it on the mouse-over event):

.closebox {
  display: none

.tab:hover .closebox {
  display: block;

.tab {
  padding-top: 0px;
  padding-bottom: 0px;

You can make .tab even tighter:

.tab .icon {
  padding-top: 2px; /* reducing it by 2px */
  padding-bottom: 2px;

:root {
  --tab-height: 22px; /* reducing it by 4px */



It might not be the direct answer but a suggestion. You don't have to fully disable this section while not all of the sub-sections have shortcuts to bring them to the foreground. Instead you can use this css in ~/.mozilla/firefox/???/chrome/userChrome.css to shrink it.

#sidebar-header {
  font-size: 1em !important;
  font-weight: normal !important;
  padding: 0px !important;

Give a chance to Stylish it is a plugin (FF, Chrome) that enables you to modify the appearance of any website.

  • 1
    I don't believe the currently available version works with Firefox V57+.
    – fixer1234
    Oct 14, 2017 at 17:23
  • There's a WebExtension version of Stylish now, but it doesn't really help with this; it's geared towards restyling page content, but the question at hand is about altering the Firefox browser chrome.
    – Darael
    Nov 30, 2017 at 14:50
  • I have it running now with v58.0.2 (64-bit)
    – Josem
    Mar 3, 2018 at 10:19

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