You restarted Firefox and the tab groups you built are gone. That usually means Firefox is not restoring your last session, it was force-quit before it could save, or a tab extension is rewriting the groups on load.
Work through the fixes in order: restore the previous-session setting, confirm Tab Groups is on, rule out tab extensions, and if the session file is damaged, copy one of Firefox's automatic backups back into your profile.
In this guide, I have covered:
Contents
Why Your Firefox Tab Groups Are Missing After a Restart
You restart Firefox, and the groups you arranged on the tab strip are not there anymore. The tabs may load fine, but the labels, colors, and groupings are gone.
Firefox Tab Groups is a built-in feature that bundles related tabs under a single colored label. When it works, opening Firefox again brings those groups back exactly as you left them.
When they vanish, the cause is almost always one of three things: Firefox is not set to restore the previous session, the browser was force-quit before it could write the session file, or a tab extension is breaking the group structure on load.
Mozilla tracks this in their support pages, including a community discussion of tab group persistence that covers the recurring cases. The fixes below walk the same ground in step form, starting with the most common cause.
Make Sure Firefox Restores Your Previous Tabs
If your groups disappear after every restart, check this setting first. Groups live inside the session that Firefox saves, so a startup setting such as your home page or a blank page throws them away silently.
- Click the hamburger menu
at the top right of Firefox and choose Settings. - Select the General panel from the left sidebar.
- Scroll to the Startup section.
- Tick the box next to Open previous windows and tabs.
- Also tick Warn you when quitting the browser below it, so Firefox prompts you next time instead of dropping the session silently.
Restart Firefox once after changing the setting. You’ll know it worked when the windows, tabs, and groups from your last session all come back together.
If Firefox still opens a blank page, reopen Settings and confirm the radio button next to Show your windows and tabs from last time is actually selected.
Private windows are the exception. Firefox never restores them, so they stay out of the session you are trying to protect. Want a throwaway window that will not disturb your groups? Open a private window instead.
Make Sure Tab Groups Is Turned On
Groups that never come back at all, even in the session where you created them, point to the feature being off. Tab Groups ships enabled in newer Firefox releases, but a profile reset, a corporate policy, or an older installation can leave the toggle switched off.
With the toggle off, Firefox ignores the saved group structure on restart and returns your tabs ungrouped.
- Click the menu and choose Settings.
- In the General panel, scroll to the Firefox Labs section.
- Toggle Tab Groups on.
- Close and reopen Firefox to confirm the setting sticks.
TIP: If the section is missing, you can also flip the preference directly: visit about:config in the address bar, accept the warning, search for browser.tabs.groups.enabled, and set it to true. Restart Firefox after changing it.
If you have been poking around in settings and are not sure what else got switched along the way, resetting Firefox settings to their defaults gives you a known starting point before you dig further.
Disable Extensions That Manage Tabs
Tab extensions are the next suspect. Simple Tab Groups, Tab Session Manager, OneTab, and similar tools work by taking over how Firefox stores and restores tab state, and Mozilla’s support note warns they can leave tabs ungrouped or placed in the wrong group.
- Click the hamburger menu at the top right of Firefox.
- Click Help.
- Select Troubleshoot Mode….
- Click Restart in the confirmation dialog.
You’ll know it worked when your groups come back inside Troubleshoot Mode. If they survive there but break again as soon as you re-enable extensions, a tab add-on is the culprit. Disable or remove the tab-management extensions you no longer need, restart Firefox, and recreate the groups you care about.
Always Close Firefox Cleanly
Firefox writes the session record (the file that remembers groups, tabs, and windows) only during a normal quit. End the process from Task Manager or Activity Monitor, run kill, or cut the power, and the next launch has nothing to restore from.
Let Firefox close on its own terms:
- Click the menu in Firefox.
- Choose Exit (Windows and Linux) or Quit Firefox (macOS) instead of closing the last window.
- Wait a moment for the process to disappear from the system tray or the Dock before walking away from the computer.
If you shut down the computer while Firefox is still open, give Firefox a few seconds to close on its own. Some shutdown flows force-kill processes after a short grace period, which can wipe the session file.
Recover Lost Tab Groups From Sessionstore Backups
If Firefox crashed or was force-killed, the session file in your profile may still hold your old groups. Firefox keeps a small rolling set of automatic backups that you can copy back into place before the next launch.
- Type about:support in the address bar and press .
- Under Application Basics, find the Profile Folder row and click Open Folder (or Open Directory on macOS).
- Open the sessionstore-backups subfolder inside the profile.
- Look for files named recovery.jsonlz4, recovery.baklz4, previous.jsonlz4, and the dated upgrade.jsonlz4-yyyymmddhhmmss backups.
- Close Firefox completely before touching any of these files.
- Copy the backup you want to recover to the parent profile folder and rename it to sessionstore.jsonlz4, overwriting the broken file.
- Restart Firefox. The backup loads as the current session.
Start Firefox once after copying the backup in. You’ll know it worked when the recovered session opens with your groups intact. Leave it open, save the tabs you cannot afford to lose as bookmarks, and let the new session file overwrite the broken one.
Refresh Firefox as a Last Resort
If nothing above brings your groups back, the session file in your profile may be permanently corrupted. A Refresh reinstalls Firefox’s internal data while keeping your bookmarks, passwords, and most settings, which gives the session file a clean slate.
- Click the hamburger menu , choose , then select .
- On the Troubleshooting Information page, find the Give Firefox a Tune Up section on the right.
- Click Refresh Firefox and confirm by clicking in the dialog.
- Wait for Firefox to restart. Your bookmarks and logins are preserved, but extensions and most site settings are reset.
Recreate your groups after the refresh and restart Firefox to confirm they survive. If they do, the previous profile’s session data was the problem. If even a brand-new profile will not keep groups, file a bug on Bugzilla so Mozilla can investigate.
Tab groups are local only and do not sync between devices or Firefox profiles. Even with a signed-in Firefox Account, a group you create on your laptop will not appear on your phone or another computer. If you need access to the same set of tabs across devices, save the group as a bookmark folder or use a tab sync extension built for that job.
Frequently Asked Questions
Why don’t my Firefox tab groups sync to my phone or another computer?
Tab groups in Firefox are stored locally inside your profile and are not part of Firefox Sync. Even with a Firefox Account signed in on every device, the groups stay on the machine where you created them.
Are Firefox tab groups saved in the cloud?
No. The group structure is saved alongside your other profile data on the local disk, inside the sessionstore files. A Firefox Account does not back up groups, and reinstalling Firefox on the same machine does not recover groups from a cloud copy.
How do I get my tab groups back after a crash?
Firefox keeps several automatic copies of the session file in the sessionstore-backups folder inside your profile. You can replace the current sessionstore.jsonlz4 with one of those backups before the next launch, which restores the tabs and groups that were open at the time of the backup.
Do Firefox tab groups work on Android?
Tab Groups is a desktop feature in current stable Firefox for Windows, macOS, and Linux. Mozilla has not yet shipped Tab Groups to Firefox for Android as a default feature, so the toggle is not available there today.
Why does Firefox keep grouping my tabs on its own?
Some tab extensions aggressively re-group or un-group tabs on load, and a few sites trigger group suggestions through Firefox Labs experiments. Running Firefox in Troubleshoot Mode is the fastest way to confirm whether an add-on is responsible, since it disables extensions and themes for the current session.
Once your groups survive a clean restart, they will keep surviving as long as Firefox is allowed to close normally and no tab add-on interferes. If they vanish again, recheck the startup setting first, because that is where most cases end.
