Tree Style Tabs is an excellent plugin and probably the main reason I use Firefox. With the newer versions of Firefox, Tree Style Tabs works nicely, but I can still see the same tabs duplicated across the top horizontally.

How can I hide the horizontal Tab Bar until Firefox incorporates this functionality?

Plugin Firefox Page: https://addons.mozilla.org/en-US/firefox/addon/tree-style-tab/
Plugin Homepage: http://piro.sakura.ne.jp/xul/_treestyletab.html.en

  • those with big screens might also like Tab Center Redux as it looks bigger then tree style tabs.
    – Vitas
    Commented Jan 11, 2018 at 20:07

1 Answer 1


The horizontal tab bar can be hidden with the following steps:

  1. Confirm or Create:
    Linux: ~/.mozilla/firefox/<profile name>/chrome/userChrome.css
    Windows: %AppData%\Mozilla\Firefox\Profiles\<profile name>\chrome\userChrome.css
    macOS: ~/Library/Application Support/Firefox/Profiles/<profile name>/chrome/userChrome.css
  2. Add the Following code to: userChrome.css
    @namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");
    #TabsToolbar {
        visibility: collapse !important;
    ^Note: Line 1 is required when creating the file and does not need to be included more than once.
  3. Restart Firefox

As this is a custom workaround until either Firefox itself allows the horizontal tab bar to be hidden, or the TreeStyle Tabs extension itself hides it, this information may become dated in the future.

Confirmed Testing: Firefox Nightly 58.0a1 (2017-10-23) (64-bit)

As of Firefox 69: By default, userChrome.css modifications are disabled in Firefox. You need to make sure that on the about:config page in Firefox, the toolkit.legacyUserProfileCustomizations.stylesheets preference is set to true and then restart the browser. (see https://bugzilla.mozilla.org/show_bug.cgi?id=1541233)

EDIT: Added macOS. h/t: @coderuby

  • Confirmed working on 57.0 64-bit, Linux Mint.
    – Vivian
    Commented Nov 14, 2017 at 23:03
  • 1
    Works on macOS 10.11.6 with Firefox 58.0b4. On macOS the userChrome.css can be found or created under: ~/Library/Application Support/Firefox/Profiles/<profile name>/chrome/userChrome.css
    – coderuby
    Commented Nov 16, 2017 at 9:44
  • Note: if you open a new window, you'll still have to click the Tree Style Tab button if you open new tabs. Otherwise they'll be open, but hidden.
    – Anssssss
    Commented Nov 16, 2017 at 20:41
  • 4
    Users who view issue this may also want to hide the Tree Style Tabs heading that appears in the sidebar: #sidebar-header { display: none; }
    – uglycoyote
    Commented Dec 14, 2017 at 17:19
  • 2
    just FYI. I did not have a chrome folder there neither userChrome.css file! Had to create it, but it works.
    – Vitas
    Commented Jan 11, 2018 at 20:27

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