There is an extension named Bookmarks Organizer that has a feature to search for duplicates and let you delete them. I played with it once and it seemed slow, but thorough.

To kick start the process, though, if you see entire duplicate folders, you might want to remove those first (using the Library window -- Ctrl+Shift+b or "Show All Bookmarks").

https://addons.mozilla.org/firefox/addon/bookmarks-organizer/

zapatero said

Now I find that this whole hierarchy has been duplicated many times and it has become literally too messy to use.

Per chance, are you using Sync?

1. If so, you should Disconnect from Sync and then run the Integrity Check before cleaning up whatever corruption remains, if any.
2. Do that on all your devices that are using on that Firefox Account; Disconnect from Sync, run Integrity Check, and clean it up if necessary.
3. And before reconnecting to Sync on any device change your Firefox Account Password to clear your data from the Sync server.
4. Then you can Connect the first device (not a Mobile device) to Sync.
5. After that - one at time Connect your other devices to Sync, but don't do it immediately as it may take some time for the Sync server to digest connecting each device and getting each synchronized again.

Thank you for your reply edmeister By "Sync" do you mean an app specifically named "Sync"? I am not doing any syncing -- so that should make my problem easier to solve, one would think; however, I have already run the Integrity check and it didn't help.

What would you think about this:? If I remember correctly, one could just delete the folder in Opera, and then it would grow a new one on the next use. Is that possible with Firefox? I could then Import my Bookmark file from another Firefox. It wouldn't be the same, because I haven't been Sync-ing, but it would be good enough. Your thoughts?

jscher2000 said

There is an extension named Bookmarks Organizer that has a feature to search for duplicates and let you delete them. I played with it once and it seemed slow, but thorough. To kick start the process, though, if you see entire duplicate folders, you might want to remove those first (using the Library window -- Ctrl+Shift+b or "Show All Bookmarks"). https://addons.mozilla.org/firefox/addon/bookmarks-organizer/

Thank you for your reply, jscher

I have read your link re Bookmarks Organizer. Then I read all the user critiques, and frankly they rather scare me. I fear that I might well make my mess even worse.

Then I attempted your second suggestion, but for some reason mine are all "greyed out" so I cannot even access them to delete them!

What would you think about this:? If I remember correctly, one could just delete the folder in Opera, and then it would grow a new one on the next use. Is that possible with Firefox? I could then Import my Bookmark file from another Firefox. It wouldn't be the same of course, because I haven't been Sync-ing, but it would be good enough. Your thoughts?

If you use Sync then best is to disconnect Sync while performing maintenance/repair efforts to files in the Firefox profile folder.

You can check the automatically created bookmarks backups in the bookmarkbackups folder to see if there is a sudden rise in the number of bookmarks.

• Bookmarks -> Show All Bookmarks -> Import & Backup -> Restore

The name of an automatically created JSON bookmarks backup in the bookmarkbackups folder 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.

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

• use "Verify Integrity" on the "Help -> Troubleshooting Information" (about:support) page

See also:

• http://kb.mozillazine.org/Locked_or_damaged_places.sqlite
• https://support.mozilla.org/en-US/kb/Bookmarks+not+saved#w_fix-the-bookmarks-file