Sidebar and Vertical Tabs Launch in Release 136

[asafko]

Hi folks! The updated sidebar and vertical tabs are now rolled out and available to all release users on Firefox 136.

How to enable it
Go to Firefox Settings → General → Browser Layout and check Show sidebar. Then, choose the settings icon in the sidebar to customize which tools appear. You can turn on vertical tabs from sidebar settings or simply right-click on the Firefox toolbar or tab strip and select Turn on Vertical Tabs.

Firefox Settings: Browser layout

Customize sidebar options

Key improvements

✅ Horizontal tab users can now hide and show the sidebar with one click using the sidebar toolbar button.

✅ Sidebar settings have been streamlined, making customization easier.

✅ Close vertical tabs in one click without expanding them. The close button now appears when hovering over a tab favicon.

✅ We’ve removed auto-collapse behavior of vertical tabs, as it proved cumbersome for many folks. 

What’s next? 

We’re working on more improvements to enhance the sidebar and vertical tabs experience. Some top priorities include:

• Remembering your last opened sidebar panel. When you hide the sidebar and then reopen it, the last opened panel will already be expanded. We hope to ship this as soon as Firefox 137 (April 1).
• More sorting options for history and better keyboard navigation, to match the functionality of the previous sidebar version.
• Expanding vertical tabs on hover for easier navigation.

As usual, we appreciate your patience and continued use as we refine these features and experiment to help us get to a better, more polished experience. 

[Agentvirtuel]

Apparently, a similar subject https://bugzilla.mozilla.org/show_bug.cgi?id=1927457

[gps67]

147.02 Vertical Tabs should be 20 char wide, but after restart are 1 char icon wide
Fix is settings / Browser Layout / Horizontal Tabs # then Vertical Tabs

[Jotaf]

This is a great feature! But there are a few bugs:

- "Expand on hover": Sometimes stops working and the sidebar just does not expand on hover. I couldn't find a pattern, perhaps when expanding/contracting rapidly and/or on new tab. Clicking twice on Expand sidebar resets its state and fixes it, but definitely not working as intended.

- Fullscreen (F11) normally hides the tabs, but not with vertical tabs. This is a bit of a regression.

- "Expand on hover" when minimized shows tab icons - this is unlike the "Expand sidebar" button, which (when off) hides them completely. It would be good to respect a combination of the two, i.e. if the button is off and the bar is not hovered it would be hidden (not show icons).

[Agentvirtuel]

Hello

Take a look at https://connect.mozilla.org/t5/discussions/phasing-out-the-older-version-of-firefox-sidebar-in-2026/...

@asafko wrote:
Full screen mode doesn’t hide sidebar tools (planned) https://bugzilla.mozilla.org/show_bug.cgi?id=1927457

For information.
https://connect.mozilla.org/t5/discussions/sidebar-and-vertical-tabs-launch-in-release-136/m-p/11567...

[Jicetus]

The sidebar is a massive leap forward, especially used together with the split-view functionality:)

However, for users with multi-monitor setups (e.g., one landscape and one portrait), the global sidebar setting can be limiting. Would it be possible to explore any of these?

• Per-window sidebar toggling (enable/disable independently per window)?
• A "main window" mode (sidebar only appears in one designated window)?
• Conditional display (e.g., sidebar only appears if window width exceeds a set threshold)?

Would help optimize screen real-estate, especially for users with constrained monitor widths. If this won't be coming down the pipeline, is there a workaround that could achieve similar functionality?