Phasing Out the Older Version of Firefox Sidebar in 2026

[asafko]

Hi folks, 

Over a year ago, we introduced an updated version of the sidebar that offers easy access to multiple tools – bookmarks, history, tabs from other devices, and a selection of chatbots – all in one place. As the new version has gained popularity and we plan our future work, we have made a decision to retire the older version in 2026. 

Old sidebar version

Updated sidebar version

I know that changes like this can be disruptive – especially when they affect established workflows you rely on every day. While use of the older version has been declining, it remains a familiar and convenient tool for many – especially long-time Firefox users who have built workflows around it. 

Unfortunately, supporting two versions means dividing the time and attention of a very small team. By focusing on a single updated version, we can fix issues across the Firefox frontend more quickly, incorporate feedback more efficiently, and deliver new features more consistently for everyone. For these reasons, in 2026, we will focus on improving the updated sidebar to provide many of the conveniences of the older version, then transition everyone to the updated version.

Here’s what to expect:

• Starting with the late Firefox Nightly 148, we have turned on the new sidebar by default for Nightly users. The new default will remain Nightly-only for a few releases to allow us to implement planned improvements, existing community requests, and collect additional feedback.  
• In Q2 2026, all users of the older version in release will be migrated to the updated sidebar. After the switch, for a period of time, we will keep the option to return to the older version to support folks who may be affected by bugs we fail to discover during Nightly testing. During this period, you will still be able to temporarily switch back to the old sidebar by going to Firefox Settings > General > Browser Layout and unchecking the Show sidebar option. 
• In Q3 2026, we will fully retire the original sidebar and remove the associated pref as we complete the transition.

Our goal is to make our transition plans transparent and implement suggested improvements that are feasible within the new interaction model, while preserving the speed and flexibility that long-time sidebar users value. Several implemented and planned improvements to the updated sidebar were informed by your feedback, and we expect that to continue throughout the transition: 

• Hide sidebar launcher on panel close if it was hidden prior to panel open (planned)

• Full screen mode doesn’t hide sidebar tools (planned)

If you’d like to share what functionality you’ve been missing in the new sidebar and what challenges you’ve experienced when you tried to adopt it, please share your thoughts here or file a bug in Bugzilla’s Sidebar component, so your feedback can continue shaping Firefox. And if you have a chance, please consider peeking at the existing metabug to see what improvements are already on our radar. 

[darora]

Going to echo what a lot of other users have already said - the new design adds wasted space. The only thing I use on my sidebar right now is tree-style tabs. All the other buttons that were presented in the new sidebar design are ones I don't use and removed. But there's no option to remove the 100px (or whatever the exact size is) sidebar entirely, and leave just my tabs list there. It's a constant reminder that there's space that didn't need to be used on showing essentially an empty, unutilized grey box.

[wzk]

The new sidebar is only nice if you use the "vertical tabs layout" in which case the sidebar content is effectively moved to a sandwich menu in the bottom left (showing it's not needed in the first place)

But the reason why I switched from Chrome to Firefox more than 10 years ago is TreeStyleTab. So I'm not using the builtin vertical tabs (and can't yet, it's really unreadable and can only fit 30 tabs). 

Could you make room for this use case of having an extension providing it's own vertical tabs ?

[sclem]

Hi, I'd like to understand why you think vertical tabs can only support 30 tabs? That's simply not the case; scrollbars are used when tabs overflow. You might want to check your system level scrollbar setting. Are they unreadable for you because of the font size? More details (screenshots and or screencasts) will help us improve this surface. Also noting that in vertical tabs mode you need to hit the sidebar toolbar button (or its shortcut) to toggle the sidebar from the collapsed state where you only see tab icons, to wider where you can see tab titles. You can also drag it wider or narrower.

Additionally, you can still use Tree Style Tabs with the new sidebar - there is no change to behavior in that respect, even in vertical tabs mode. Is the ask to be able to hide vertical tabs and only the TST panel showing?

[wzk]

I can still use TST but only on top of previous tabs
See screenshot: 

I prefer TST over builtin vertical tabs for a number of reason, but yes they do use too much vertical space (I know what scrollbars are thank you), and the contrast between text and bg is often not enough.

[asafko]

Hi folks, 

Thank you for continuing providing feedback and stress testing the keyboard navigation as we improve it, in particular. The delete keyboard action is accessible in the sidebar, please see this demo. 

We have also planned to support a setting that allows you to switch to the dropdown navigation instead of the launcher, here's the rough demo.

This setting (Hide sidebar is a temporary name) will become available in Nightly, and eventually, release in version 154 and 155.

Long-term, we plan to make the sidebar a part of the customizable UI, so any website or browser action/destination can be added to it – similarly to how it's possible to add any action / website to the toolbar / bookmark toolbar. This has been by far the most requested improvement to the old and new sidebar, and the reason we've changed the interaction model. We do understand that subjective preferences on these matters differ, and want to provide an option to those of you who don't to wait until we implement this functionality or don't need it at all, and prefer the current dropdown model. 

[G-]

I was using the new sidebar extensively but I just tried the old sidebar and I actually really like it. One thing I like about the old sidebar is the ability to have the history collapsed when opening it (Ctrl+H). I only use it for search and I don't want my recent history staring at me every time I open the history sidebar, I find it distracting.

I also tried Tree Style Tab and, compared to the new sidebar with vertical tabs enabled, when opening Tree Style Tab on some pages (by pressing the Tree Style Tab button), the page gets resized in a way that seems slightly less jerky than the way the page is resized when opening the new sidebar (by clicking the sidebar button or enacting the keyboard shortcut) with vertical tabs enabled. This is because Tree Style Tab pops up whereas the new sidebar with vertical tabs slides in from the side when the button or shortcut is pressed. History and Bookmarks (in the new sidebar or the old sidebar) also pop up in the same way as Tree Style Tab. Doing it this way for the vertical tabs in the new sidebar as well would make them more consistent with the other interface elements. I will not be sticking with Tree Style Tab however, as I don't need to use it. It is also slightly redundant as it is not possible to hide the default browser tabs whilst using it (but maybe the tree functionality from Tree Style Tab is something to implement in Firefox vertical tabs, as it's useful – note that it is different from Tab Groups as Tab Groups does not display tabs as children of other tabs and therefore it does not display tabs that were opened using 'Open in New Tab' as a child of another tab automatically, which are things that are done by Tree Style Tab, as well as it giving the ability to collapse children and only show parents, all of which help organisation).

[G-]

---

@G- wrote:

I was using the new sidebar extensively but I just tried the old sidebar and I actually really like it. One thing I like about the old sidebar is the ability to have the history collapsed when opening it (Ctrl+H). I only use it for search and I don't want my recent history staring at me every time I open the history sidebar, I find it distracting.

---

...Having said that, it's not possible to collapse the history when sorting by last visited in the old sidebar. It would be good if you added the ability to collapse the history in general in the new sidebar, to just use the history search functionality.