Recover Firefox Data Missing After an Update or Profile Change

Firefox restarted after an update and now your bookmarks, saved logins, history, or extensions look gone. In most cases nothing was deleted. The browser is opening a different profile, and your old one is still on disk.

Compare the profiles Firefox lists, make the one with your data the default, test it in a new window, and back it up. Then check the update settings so the next update does not surprise you the same way.

In this guide, I have covered:

Firefox updated without asking, and now your data looks gone

You never clicked Update. Firefox restarted anyway, and the bookmarks bar is empty, saved logins are missing, and your extensions are gone. Take a breath: in most cases nothing was deleted.

Firefox installs updates in the background, and recent releases ship a redesigned profile manager. After the restart, Firefox can come up on a different profile, and each profile keeps its own bookmarks, history, saved logins, extensions, and settings. Your old data is still sitting on the disk.

An update is not proof that Firefox erased anything. Profile entries often carry generated names like ABCD1234.Profile 1, so compare them with Mozilla’s official profile management guide before you change a single setting.

Do not delete an unfamiliar profile, clear data, reinstall Firefox, or create a replacement profile until you have compared the available profiles. A backup is safer than destructive testing.

Check which Firefox version is installed

Before you touch profiles, confirm which build is actually running. A version number newer than the one you remember installing means an update really did land.

1. Click the hamburger menu at the top right of the Firefox window.
2. Choose Help, then select About Firefox from the submenu.
3. Look at the line under the Firefox logo that says "Version". The number next to it is your current version.
4. Alternatively, type about:support in the address bar and press Enter. The Version field appears under Application Basics.

You’ll know it worked when Firefox displays the version number. That confirms the update happened. It does not tell you which profile holds your bookmarks, so keep going.

Open the Firefox profile manager

Next question: which profile is Firefox using right now? The internal profile manager answers that and lists the alternatives Firefox still recognizes.

1. Open a new Firefox tab.
2. Type about:profiles into the address bar.
3. Press Enter.
4. Open Manage Profiles if the profile entries are not already visible.

You’ll know it worked when the page lists the current profile at the top, with other entries below it. Leave that tab open while you compare them.

Check each profile for your Firefox data

Don’t judge by the first screen. Pick one bookmark folder, saved login, history entry, or extension you know well, then look for it in every profile you recognize.

1. Type about:profiles into the address bar and press Enter.
2. Review the This is the profile in use section and any Other profiles listed below.
3. Note the path of the profile you usually use, and check whether the desktop you are looking at matches.
4. Click Launch profile in new browser next to the profile you want to inspect.
5. In the new window, open about:logins and search for the missing entry.

You’ll know it worked when one profile shows that familiar item. That profile is your recovery target. Leave the empty-looking one in place until you have checked the rest.

Make the correct profile the default

Finding the right profile is half the job. The other half is making Firefox open it every time, so the next restart does not drop you back into the empty one.

1. Type about:profiles into the address bar.
2. Press Enter.
3. Select the profile that contains the recognizable data.
4. Select Set as default profile.
5. Select Launch profile in new browser.

Success check: the new window should show your familiar bookmarks, history, saved logins, and extensions. Keep the old window open until it does.

What to do if the old profile is not listed

Sometimes the profile you want does not appear at all, and that is exactly when people make things worse by creating a new one. Restart Firefox once first. Mozilla’s redesigned manager is generally available, but older profiles do not always show up immediately.

1. Close all Firefox windows.
2. Quit Firefox if it remains open.
3. Start Firefox again.
4. Type about:profiles into the address bar.
5. Press Enter.
6. Review every profile group, including Other profiles.
7. Type about:editprofile into the address bar.
8. Press Enter.

The direct profile page can still show an older profile even when the normal menu hides it. If a profile you had not seen before contains your data, go back and set it as the default. If none of them do, stop creating or deleting profiles and leave the existing ones untouched.

Back up the recovered Firefox profile

Do this before you reset settings, change Sync, or try any other repair. A backup file is your undo button if a later step goes wrong.

1. Reopen about:profiles.
2. Select the recovered profile.
3. Open the options for that profile.
4. Choose the backup-to-file action.
5. Choose a destination outside the live profile folder.
6. Wait until Firefox reports that the backup is complete.

Success check: the file exists where you put it, and it stays there until you have verified the recovered bookmarks and saved logins.

Mozilla documents the built-in profile-to-file backup for Windows 10 and 11, including the new profile manager. If the action is not shown on another desktop system, follow the platform-specific instructions in Mozilla’s linked profile guide instead of creating a replacement profile.

ALERT: A profile backup may contain saved logins and other personal information. Keep it in a protected location and do not attach it to a public support post.

Confirm which Firefox data returned

One bookmark proves the right profile opened. It does not prove everything came back. Check each category before you relax.

• A bookmark folder you can identify.
• A saved login you recognize.
• Older browsing history entries.
• Previously installed extensions.
• Expected site settings or open tabs.

If the profile looks correct, do not clear site data or reset Firefox as a test. Those actions skip the profile question entirely and make recovery harder. If a site misbehaves later, clearing cookies and cache is routine once the backup file is safely on disk.

Restore missing bookmarks from a backup

Right profile, right logins, but a bookmark folder you use daily is still absent? Firefox keeps automatic bookmark backups, and one of them may still hold it.

1. With the Library open, click Import and Backup in the top toolbar.
2. Hover over Restore to open the submenu.
3. Pick the most recent dated backup that still contains your bookmarks. Entries are listed newest first.
4. Confirm the replacement prompt. Firefox overwrites the current bookmarks file with the snapshot.

You’ll know it worked when the folder reappears in the Library. If the newest backup does not contain everything, compare an older one rather than overwriting the newer copy.

Recover tabs or windows that did not reopen

Your data is back, but the tabs from your last session are not. Firefox keeps sessionstore backups on disk, and you can roll back to an earlier one.

1. Type about:support in the address bar and press Enter.
2. Under Application Basics, find the Profile Folder row and click Open Folder (or Open Directory on macOS).
3. Open the sessionstore-backups subfolder inside the profile.
4. Look for files named recovery.jsonlz4, recovery.baklz4, previous.jsonlz4, and the dated upgrade.jsonlz4-yyyymmddhhmmss backups.
5. Close Firefox completely before touching any of these files.
6. Copy the backup you want to recover to the parent profile folder and rename it to sessionstore.jsonlz4, overwriting the broken file.
7. Restart Firefox. The backup loads as the current session.

You’ll know it worked when the restored window shows the tabs you expected. Keep your current windows open until you have checked them.

Check whether saved logins were synced

Everything is back except one saved password. That points at Firefox Sync rather than the update, so check whether your logins were ever uploaded to the account.

1. Open the hamburger menu and choose Settings.
2. Click Sync in the left sidebar, or click the Mozilla account icon at the top right of the page.
3. Sign in to your Mozilla account if you are not already signed in.
4. Click Manage Sync to see the categories being shared.
5. Make sure the Logins toggle is turned on.
6. Click Sync Now to pull the latest saved logins from the cloud.

Treat the result as a status check. Sync cannot recreate a local login that was never uploaded in the first place.

Review how Firefox handles updates

With your data recovered, decide how much control you want over the next update. The controls live in Settings, and they have changed over the years.

1. Open the menu.
2. Select Settings.
3. Select General.
4. Scroll to Firefox Updates.

Ignore older instructions that tell you to choose Never check for updates. Current Firefox Settings no longer include that option, and Firefox can still update on its own. On a work machine, an operating-system package or an organization’s policy may control updates too.

Avoid a reset while you are still comparing profiles

Resetting is the step that turns a profile mix-up into real data loss. Don’t clear Firefox data, don’t remove an unfamiliar profile, and hold off on any broad reset while you are still looking for the old one.

If preferences still need attention once the recovered profile is backed up, Reset Mozilla Firefox Browser Settings on the Computer works as a separate, later step.

RELATED: Download the Mozilla Firefox and Update it to Latest Version