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Firefox deleted addon settings, its own settings and opened tabs after system crash, any way to restore them?

  • 10 svar
  • 1 har dette problemet
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  • Siste svar av jscher2000

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After a system crash Firefox loaded using default settings - everything in Options and my own edits in about:config are gone, all addon settings were reset to default, and Firefox did not load my previous session - instead of hundreds of tabs I had it loaded less than 10. It also did not ask me to restore a previous session.

Any way to fix this?

All Replies (10)

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I did have session manager addon which could have at least restored my tabs, but since all addon settings were lost, well, Firefox made it kinda useless...

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FredMcD said

Look on your desktop. Do you see a folder called; Old Firefox? Look inside. Look for the folder with the latest creation date. https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles https://support.mozilla.org/en-US/kb/how-run-firefox-when-profile-missing-inaccessible
Note: Because your preferences and extensions are often the causes of problems, this article does not explain how to copy these between profiles. Therefore, if you follow the steps in this article, you will have to reinstall your extensions and reconfigure your Firefox preferences afterward.

Yeah no, no thanks. This is stupid. My extensions are already installed, while this procedure asks me to wipe them all and configure from scratch while my main concern is restoring lost extension settings.

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Did Firefox create a new profile?

You can open the about:profiles page via the location bar to check whether multiple profiles are present and what profile Firefox currently is using.

See also "Determine if Firefox has created a new profile":


Firefox 67 and later can use a dedicated profile for each of the Firefox update channels and will lock the profile, so it can only be used by Firefox in a specific installation folder. For Release versions this profile would be a xxxxxxxx.default-release profile, profiles used in older Firefox versions usually used a xxxxxxxx.default profile (a refresh adds a time stamp).

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Anyway, I tried creating a blank profile and copying some files from an already existing profile into it - this did nothing. I still get the reset Firefox settings, extension setting that are copied are still default, no Tampermonkey scripts, no uBlock rules, nothing.

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cor-el said

Did Firefox create a new profile?

No. I still have all bookmarks and extensions. It just wiped all extension settings and Firefox own settings in about:config

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Hi Shajirr, did you already check your profile folder for other session history files that might contain your missing tabs?

If you could, please start backing up all existing files:

Do not exit Firefox, or if you closed it, don't re-open it.

(1) To open your profile folder...

If Firefox is still running:

You can open your current Firefox settings (AKA Firefox profile) folder using either

  • "3-bar" menu button > "?" Help > Troubleshooting Information
  • (menu bar) Help > Troubleshooting Information
  • type or paste about:support in the address bar and press Enter

In the first table on the page, click the "Open Folder" button.

If Firefox is closed:

Type or paste the following into the Windows Run dialog or the system search box and press Enter to launch Windows Explorer:

%APPDATA%\Mozilla\Firefox\Profiles

In that folder, do you see a semi-randomly-named folder? If so, click into it. If you find multiple such folders, find the one that was most recently updated.

(2) Copy out session history files

In your profile folder, double-click into the sessionstore-backups folder. Save all files here to a safe location such as your Documents folder.

(3) What files did you find?

The kinds of files you may find among your sessionstore files are:

  • recovery.jsonlz4: the windows and tabs in your currently live Firefox session (or, if Firefox crashed at the last shutdown and is still closed, your last session)
  • recovery.baklz4: a backup copy of recovery.jsonlz4
  • previous.jsonlz4: the windows and tabs in your last Firefox session
  • upgrade.jsonlz4-build_id: the windows and tabs in the Firefox session that was live at the time of your last update
  • some old .js files from Firefox 55 or earlier

Could you take a look at what you have and the date/time of the various files to see whether you think any of them would have the missing tabs?

To preview the contents of a file, you can drag and drop it onto this page, then click Scrounge URLs: https://www.jeffersonscher.com/ffu/scrounger.html

That tool is on my site, so please let me know if it doesn't work for you.

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jscher2000 said

Hi Shajirr, did you already check your profile folder for other session history files that might contain your missing tabs?

I'll save your reply for later if I'll run into a similar problem, but for now I was actually able to restore the tabs - first time after crash Firefox didn't offer to restore anything so I thought tabs were gone.

I did make backup of the whole profile folder just in case.

However, once I closed FF and opened it again - then it did offer session restore, and restored all the tabs.

Now, only Firefox settings and extension settings are reset.

Also, turns out it wasn't just me, a bunch of other people had the exact same issue at the same time: https://www.reddit.com/r/firefox/comments/c03ttb/restarting_comp_resets_firefox_and_every_addon_in/

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Shajirr said

However, once I closed FF and opened it again - then it did offer session restore, and restored all the tabs.

Wow. That's lucky!

Also, turns out it wasn't just me, a bunch of other people had the exact same issue at the same time:

Why are people having so many system crashes? Well, a question for another thread.