Well, if you don't mind, let's get the logs of your computer and can you confirm that you are using Firefox Sync?

1. Open a new tab or window
2. In the url bar, enter about:sync-logs
3. Copy the contents of the last 5 files listed on that page, you can click on them to show the contents.
4. You can paste them in a response or in this tool https://pastebin.mozilla.org/ - just make sure to change the time span on the bottom right, a new url will be created in the url bar when you save it, copy that link and also put it in your response.

As for the deduplication https://addons.mozilla.org/en-US/fire.../bookmark-dupes/

Also if you do not mind, we have an open bug for Firefox for Android where this happens, it would be really helpful if you can share the devices that are connected to the sync account and what versions they are (Operating system version and Firefox version)

Hallo!

I pasted the 5 last logs now, I am not sure if I understand the "time span" think, if something is not right, just tell me so I do it again. There are two devices curently connected to Firefox, one is win7 the other one win8 and they both have the very last Firefox version, Deduplicating is one thing, but how can I stopp this from happening?

Thanks, M0lly

Are you using Sync to sync the bookmarks or use another sync service?

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

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

You can try to restore an older bookmark backup.

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

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 that prevents resaving the same backup.

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

Before you go, do you have url that was created? Maybe you can copy and paste the contents directly into a response?

Thank you.