After backing up the autobackups, I restored the one from very early this AM. So far so good - only the bookmarks I added today are missing.

If you have sync, and there is a problem anywhere, Shut Down Sync Immediately On All Devices to prevent the problem from spreading. Once the problem is fixed, perform the same repair on all computers/profiles before using sync again.

[v57+] Places Maintenance is built into Firefox.

Type about:support<enter> in the address bar.

You will find Places Database near the bottom. Press the Verify Integrity button.

If any errors are reported, check this link: https://support.mozilla.org/en-US/kb/fix-bookmarks-and-history-will-not-be-functional

The places.sqlite file contains your History and Bookmarks. And it looks like it is corrupted.

Type about:support<enter> in the address bar.

Under the page logo on the left side, you will see Application Basics. Under this find Profile Folder. To its right press the button Show Folder. This will open your file browser to the current Firefox profile. Now Close Firefox.

Locate the above file. Then rename or delete it. Restart Firefox. The browser should then create a new place.sqlite and recover your bookmarks from the backup files.

Note: Your history is not backed up and will be lost.

Did you already closed and restarted Firefox today?

If that isn't the case then try "Organize -> Undo (Ctrl+Z)" in the Bookmarks Manager (Library) until you see the lost bookmarks or the button is disabled.

I did close and restart firefox after this issue took place. Re the integrity check I translate the results below as "no problem", but I can't be sure because of that last entry about vacuum

> Task: checkIntegrity + The places.sqlite database is sane + The favicons.sqlite database is sane > Task: invalidateCaches + The caches have been invalidated > Task: checkCoherence + The database is coherent > Task: expire + Database cleaned up > Task: originFrecencyStats + Recalculated origin frecency stats > Task: vacuum - Unable to vacuum database > Task: stats - The task queue was cleared by an error in another task. > Task: _refreshUI - The task queue was cleared by an error in another task.

The restore from autobackup seems to have worked. I don't see that it is reverting to the 2016 state. I think it was an issue with sync, not a corruption, from the signs.

Thank you both.

That was very good work. Well Done. Please flag your last post as Solved Problem as this can help others with similar problems.

Be sure to create a backup of the bookmarks.

Open the Bookmarks Manager; Press the Alt or F10 key to bring up the toolbar, and select Bookmarks. Hot key is <Control> (Mac=<Command>) <Shift> B. Firefox 84+ <Control> (Mac=<Command>) <Shift> O.

Once the window is open, at the top of the page, press the button labeled Import and Backup. Select Export Bookmarks To HTML, and follow the prompts and save it to a HTML file. Copy the file to another computer/profile. Repeat the instructions above, BUT select Import Bookmarks From HTML.

https://support.mozilla.org/en-US/kb/restore-bookmarks-from-backup-or-move-them

https://support.mozilla.org/en-US/kb/recover-lost-or-missing-bookmarks

Mozilla search: Import {web link}

Well this just got more interesting. First, thanks FredMcD for your support. I found some bookmarks were missing again - as before, 2016 seemed to be the time it restarted from. But other sections have the full stack of bookmarks. I have over 20k bookmarks. I'm guessing that around July 13 I booted a virtual machine that had ff sync enabled and which had not sync'd in a good while. From the signs it started to sync, and didn't complete, probably because I shut down the virutual machine. The previous restore may not have been early enough...not sure how long it would take to sync two ff instances that have year's of differences. I would like to know how to clear all of the bookmarks in sync so that I can find a fresh saved json backup to restore and begin anew. I find articles like this https://support.mozilla.org/en-US/kb/delete-sync-data-firefox-signing-out-firefox-account which are ok but that's not clearing the sync store up at mozilla. When I sign back in I don't want sync to reference anything other than the (hopefully) solid bookmarks backup json file I'm going to restore from. What I've done to get read for this:

[1] logged out all ff instances on the ff accounts page (there were at least 12, I had no idea). I'm not sure that this equates to 12 instances that had sync turned on? [2] I will only enable sync on a few select pcs going forward - all of those will be one that are booted regularly. On these pcs I'll purge the bookmarks that are in place and then enable sync [3] I've attempted to open every new (since this mid july glitch) bookmark in ff so that I can add them back to the folders they should be homed in. Took some screenshots too. [4] ??? What am I missing???

What I would do when I am sure of the plan: clear all bookmarks from sync in the cloud clear all bookmarks from my main pc restore from the best json backup I can find add back some saved bookmarks enable sync in a few days enable sync on another pc that has had all bookmarks cleared away is anything missing from this aspect?

The bookmarks/history file can only get so big, then the browser runs into problems.

I suggest you go into each Firefox profile and create a backup of the bookmarks. See instructions: https://support.mozilla.org/en-US/questions/1343798#answer-1427757

Using a Word editor, you can go thru each and manually remove old or unneeded entries. Later, you can combine them together.

Thanks again Does firefox offer the bookmark count? I did have a system for archiving bookmarks to a different profile but have not used it for several years. The main question I have right now is how can I make sure that the firefox account doesn't use any of the data stored in the cloud? I am hoping to find a clean json backup file to restore from, and I would want the cloud data that exists now, which would be somewhat scrambled, to be ignored or wiped clean in favor of the json restored bookmarks.

It seems that the only way to completely clear out the sync data in the cloud is to delete the firefox account. Would I be able to recreate the account with the same name soon afterwards?

Resetting the sync password, or changing its e-mail will remove all data from the servers. The username and password are used to create the encryption.

This is a security feature. https://support.mozilla.org/en-US/kb/ive-lost-my-firefox-sync-account-information

• I've lost my Firefox Sync account information - What to do
• I’ve forgotten, or don't have access to, my Firefox Account email address

Note: Only the data on the servers is cleared. The profile data is not changed or removed.

I reset the password to clear the sycn'd data. I've restored the clean json backup file and that part seems to be ok. On that one pc I logged in to the ff account again. Sync seemed to complete in a very short time, like 15 seconds. Telling it to sync again, it spins for a second only. I then cleared the bookmarks off of my second most used pc and logged in to the ff account. It also sync'd quickly...and it's only pulled about 10 bookmarks. Manual sync adds no more. I don't think there is a way to interrogate the mozilla data store other than to ask a 'fresh' pc to sync to it, correct? Something seems drastically wrong here. Granted I need to thin the collection of bookmarks but it seems like it's not even trying to sync. I turned off sync on the second pc just to be safe.

One thing you could do is to copy the files you need to a thumb drive and move them that way.

Yes...but does it mean I can't use sync any more? I can experiment of course; copy the bookmarks over, restore, turn on sync, see if it all works. But I am considering moving to a manual system. 99% of my updates are to my main workstation. I could copy the backups from that machine to any other machine that needs to be current, and keep sync turned off. I'd just have to bear in mind that bookmark changes to other than the main workstation would not be relayed.

Sync is quite handy. Especially when connecting different types of computers.

Let's try this:

Resetting the sync password, or changing its e-mail will remove all data from the servers. The username and password are used to create the encryption.

This is a security feature. https://support.mozilla.org/en-US/kb/ive-lost-my-firefox-sync-account-information

• I've lost my Firefox Sync account information - What to do
• I’ve forgotten, or don't have access to, my Firefox Account email address

Note: Only the data on the servers is cleared. The profile data is not changed or removed.

After, re-sync one unit at a time.

That's what I did.

Oops. And now after a reboot, my main machine has lost all of it's bookmarks. Not one remains. I'm going to turn off sync and restore the bookmarks from last night. Maybe sync itself got messed up by some recent ff updates. For example, this shows You are currently syncing these items: Bookmarks History Add-ons Settings I never had History set to sync. And when I go to change those, all the options are unchecked, and trying to check any of them doesn't change anything...the checkboxes never get a check. I just found that history has also been completely wiped.

Shut down the old sync. Then create a new account.

Type https://accounts.firefox.com/settings Near the bottom, press Delete Account.

I have had great success with firefox sync for several years, but always knew that any sync system could foul up (it'd happened with xmark before, and ff sync in the early days). I think I'll pass on ff sync. This experience has wasted a lot of my time and I can live without sync. No doubt I am responsible for the manner in which it messed up the bookmarks, but it's also been discoraging to find the control points defective or disabled. It's pretty black box...xmarks was better in that regard. I'll find a way to manually share the bookmarks. I am a bit discouraged about firefox these days. There terrible ui changes that one cannot walk away from; the profound lack of add ins in comparison with what we used to have; the lack of granularity in the control points for sync and bookmarks. But it's still the best browser out there by far. FredMcD thanks a lot for your help with this, you made a big difference. I did recover most of the bookmarks and it'd have been much harder without your input.