We see reports that the places.sqlite database file sometimes gets corrupted when you are using Sync, so this might have happened in your case.

You can check for problems with the places.sqlite database file (bookmarks, history) in the Firefox profile folder.

• Places Maintenance: https://addons.mozilla.org/firefox/addon/places-maintenance/

If the Places Maintenance extension can't repair the places.sqlite database file then remove all places.sqlite file(s) in the Firefox profile folder to make Firefox rebuild the places.sqlite database file from the most recent JSON backup in the bookmarkbackups folder.

• http://kb.mozillazine.org/Bookmarks_history_and_toolbar_buttons_not_working_-_Firefox
• https://support.mozilla.org/kb/Bookmarks+not+saved#w_fix-the-bookmarks-file

If you use Sync then best is to disconnect Sync while performing maintenance/repair efforts to the places.sqlite database.

If That isn't working then try to restore an older compressed .jsonlz4 backup that isn't affected.

• Bookmarks > Show All Bookmarks > Import & Backup
• https://support.mozilla.org/kb/restore-bookmarks-from-backup-or-move-them

The name of a JSON bookmarks backup file includes a total item count (folders and separators included) and an hash value to prevent saving the same backup more than once.

• bookmarks-YYYY-MM-DD_<item count>_<hash>.jsonlz4

Use with Extreme Caution;

Bookmark Duplicate Cleaner {web link} Scans for bookmark duplicates and allows you to delete them

Bookmarks Checker - check for bad links {web link} Check favorites for broken or bad links. It checks for bad links and displays a report if it finds something. Check for 404 links, timeout links.

cor-el said

We see reports that the places.sqlite database file sometimes gets corrupted when you are using Sync, so this might have happened in your case.

Sorry to say that ... not one of your ways worked (the old bookmarks are not old enough).

FredMcD said

Use with Extreme Caution;

Tried this too ... these addons only find 1 dupe of each, delete them and after that "Level" 2 to "Level" XXX...only shows "no title" but all other million dupes still exist and deleting them by hand deletes every entry, not only the dupe.

How many bookmarks show the backups in the bookmarkbackups folder if you check the item count part of their names?

• bookmarks-YYYY-MM-DD_<item-count>_<hash>.jsonlz4

Did you try to delete the places.sqlite file?

cor-el said

How many bookmarks show the backups in the bookmarkbackups folder if you check the item count part of their names?

In the folder - wait a sec - 5k up to 11k. (Mostly arround 5200-5300) Yes, I deleted the places.sqlite more than once.

Did you try to restore one of the compressed .jsonlz4 backup that a bookmarks count that looks correct?

Backup with a high count may be corrupted. When you delete places.sqlite then Firefox will try to restore the bookmarks from the most recent backup and if that backup is corrupted then that won't help and you need to restore an older backup.

You can also check if Places Maintenance is reporting a problem.

• https://addons.mozilla.org/firefox/addon/places-maintenance/

cor-el said

Did you try to restore one of the compressed .jsonlz4 backup that a bookmarks count that looks correct? ... When you delete places.sqlite then Firefox will try to restore the bookmarks from the most recent backup ... You can also check if Places Maintenance is reporting a problem.

There simply os not a single .jsonlz4 backup with a boomark count looking allright.

After deleting places.sqlite Firefox restores a list of bookmarks last used _before_ Mozilla changed to .jsonlz4 backup- so with mere half of last bookmarks.

The addon isn't reporting anything.