Is it possible to add a toolbar separator to Firefox ( I can't see the option;

Customise Toolbar Firefox options

Used to be available.

Old Firefox Toolbar Customisation


Is it possible to add a toolbar separator to Firefox?

To the left of the window you show in your question should be "Additional Tools and Features" which contains the available toolbar buttons. You can drag and drop these buttons onto an open toolbar.

You can install the Classic Theme Restorer add-on to get additional toolbar buttons as well as other useful features.

Classic Theme Restorer Additional Buttons

If you don't have any open toolbars to use a a drop target, then click on "Show/Hide Toolbar" at the bottom of the "Additional Tools and Features" screen.

Firefox Show/Hide Toolbar

See Customize Firefox controls, buttons and toolbars for more information.


I am not affiliated with Classic Theme Restorer in any way, I am just an end user of the software.

  • This solution does not work anymore for Firefox Quantum (Version 57) since Classic Theme Restorer is not available as an addon anymore. The solution from Aibara Iduas (manually adding the separators) still works. – Albin Jan 12 '18 at 1:24

You can add separators to Firefox's toolbars without any add-on, even with the new Photon UI. I've tested this in Firefox Nightly (currently 57.0a1). The graphical option to do so, however, was removed long, long ago.

  • Type about:config into the address bar.
  • Search for the preference with the name browser.uiCustomization.state.
  • Double-click on the value, which will allow you to edit it. It contains the placement of all the widgets/icons/etc. that Firefox uses. Place customizableui-special-separator2 (separated by commas) wherever you want a separator.
  • Restart Firefox.

In the case below I've added a separator between the new container tab and uBlock Origin buttons, so those particular values in that preference look like this: "containers-panelmenu","customizableui-special-separator2","ublock0_raymondhill_net-browser-action"

enter image description here

  • Awesome!!!! This works perfectly on Firefox Quantum 58.0.2. Additional information: I think the ID has to be unique in customizableui-special-separatorID to preserve consistence. Also Firefox needs to be restarted in order to see the modification). I really hope somebody will develop a specific Firefox extension to allow easier creation and placement of separator bars in the addon toolbar. – Sly Mat Mar 1 '18 at 7:24
  • +1 Thanks for this! Is there a similar way to do the old "spacers" (the fixed-width ones, not the flexible ones)? – istrasci Mar 15 '18 at 16:35
  • Any idea where these IDs might be documented? – Jacktose Jan 7 '19 at 23:28
  • @istrasci customizableui-special-spacer01 (again, with a unique number at the end). Just worked for me on 64.0. Needs a restart to take effect. – Jacktose Jan 7 '19 at 23:36
  • I've edited the answer: formatted steps into a list; added "Restart firefox" step. This works for 67.0.4 (64-bit). – John Bentley Jul 9 '19 at 4:16

You can right-click on the toolbar and choose "New separator" (or something similar, I don't have English version).

  • Is this still available in recent versions of Firefox? – RockPaperLizard Aug 15 '16 at 5:55

You could try on Classic Theme Restorer which would give you: Squared tabs, AppMenu, Add-on bar, small button view, and many more 'old' features for Firefox 29+. Which could help to make Firefox better

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