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.

Firefox automatically makes backups of the bookmarks. These are stored in the bookmarkbackups folder.

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.

Once the window is open, at the top of the page, press the button labeled Import and Backup. Select Restore. From the list, pick the file you want and click it.

The backups are stored in a jsonlz4 file named something like this; bookmarks-2016-06-29_1424_enD1GTH ya0JmicnYWg4V4g==.jsonlz4

In this example; 2016-06-29 = date created, 1424 = number of entries.

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

See this support article: https://support.mozilla.org/en-US/kb/restore-bookmarks-from-backup-or-move-them#w_restoring-from-backups

Firefox automatically saves 15 bookmarksbackup files in the Profile folder, one for each day that Firefox has been used. The current day and 14 days / 2 weeks of backups. So if you are using a "duplicated" Profile it should have all those backups.

As Fred mentioned, make sure that you dis-connect from Sync before doing a "cleanup/delete" process, and once you are done making changes to your set of bookmarks connect back to Sync and let Firefox run a few hours while connected to Sync so that the Sync server has time to absorb all the changes that you made.

Note that it is not one backup each day, but a new backup is only created when changes have been made to bookmarks and the calculated hash value that is part of the file name is different.

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.

One thing that you can do is to save your bookmark backups when you want, and keep them as long as you want.

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.

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.

This is precious information but I cannot apply it because my browser.bookmarks.max_backups was set to 0.

Thank you!

Firefox automatically makes backups of the bookmarks. These are stored in the bookmarkbackups folder. You can set how many backups are kept by doing this;

Type about:config<enter> in the address bar. If a warning screen comes up, press the I Accept the Risk button. At the top of the screen is a search bar. Type browser.bookmarks.max_backups

The values for this setting are; -1 = unlimited number of backups 0 = Do not create any backups Any other number here will keep that many backups Example: 5 = 5 backups are kept.

The backups are stored in a jsonlz4 file named something like this; bookmarks-2016-06-29_1424_enD1GTHya0JmicnYWg4V4g ==.jsonlz4 In this example; 2016-06-29 = date created, 1424 = number of entries.