Hi DPJ, At least you didn't lose anything.

The first thing that I would do is disconnect from Sync.

Then, unless someone has a better idea, there are extensions which can find and delete duplicate bookmarks:

https://addons.mozilla.org/en-US/firefox/search/?platform=windows&q=duplicate%20bookmarks&type=extension

Thanks for your response Robert. I’ve disabled Sync and already tried all the extensions I could find that promised help, unfortunately when I ran each of them they failed to produce any response..........just ‘loading’ until I gave up after 30 minutes or so. I’ve even tried to open one of my backup files with an extension I added, but that too just whirrs away without actually opening the file. Seems it is just too big to handle. Any further help would be much appreciated.

Forget about using "extensions" to fix that mess.

With Sync disabled: 1. In desktop / laptop Firefox installations open Help > Troubleshooting Information and near the bottom see Places Database and use the Verify Integrity button to the right. Wait for the results of that verification process, a chart of the processes will appear; that should fix the duplication of bookmarks problem on that device.

2. Then on the iPhone use Manage Account for your Firefox Account and change the Password. That will clear the corrupt data from your Firefox Account. There is no "Verify Integrity" feature on "Mobile" devices. The Sync server has that feature.

3. Then allow Firefox to run on the iPhone with the new Password.

4. Then after awhile use the new Firefox Account Password and connect that device to the Sync service; thus feeding the data from that device to the Sync server.

5. Lastly, depending upon the overall load on the Sync server it may take some time for the synchronization process to be completed, so don't expect immediate results.

I boot up my computer, start Firefox and my short list of Bookmarks has duplicated tirhgt before my eyes with literally hundreds of multiple copies of the bookmarks.

This has been a problem for me since I started using Firefox last year. I stopped sync and I am not even logged into my firefox account when using the browser. I did that BECAUSE I was constantly duplicating across devices. Bookmarks that are being restored are lists and bookmarks from literally a DECADE ago, that I have not used in years - I have no idea how these things continue to follow me around....

I read the posts about turning off Sync - well how is it that I am syncing anything if I am not logged in and there is no sync running that I can find? I am NOT logged in to my Firefox account when I am using the browser

This is truly broken, truly infuriating and I do not have the time in my day to constantly be deleting, restoring, updating, managing my bookmarks. Firefox needs to come up with a solution to this - at least a prompt of "DO YOU WANT TO SYNC" or not so users can stop this before it starts to duplicate again

I Am not happy. I will be dumping firefox shortly if this is not resolved.

Maybe you still have an older JSON backup that doesn't have the duplicates.

• 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. You also see this count in the Restore menu drop-down list.

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

See also:

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