Verify Integrity reported no problems with either places.sqlite or favicons.sqlite?

Can you add a new bookmark, or move a bookmark into a folder, or are those also failing?

I can post new bookmarks and move them, just not delete.

Do you want to check whether an add-on can delete bookmarks successfully? This one creates a sidebar for searching but also has a right-click > Delete option:

https://addons.mozilla.org/firefox/addon/bookmark-search-plus-2/

If that can't delete either, you might have to rebuild the Places database. Please make a fresh backup of your bookmarks first and check it in a new tab to make sure it looks complete. Unfortunately there is no way to back up history.

• Restore bookmarks from backup or move them to another computer (manual backup steps)
• Fix "The bookmarks and history system will not be functional" error message

I have done this, the restore will not work. Cannotr delete, add or move bookmarks. This is after a W11 rebuild. Thanks

I have done this, the restore will not work. Cannotr delete, add or move bookmarks. This is after a W11 rebuild. Thanks

It sounds like Firefox is having problems working with your "Places" database file(s).

Initial question: was this a standard install of Firefox from Mozilla's website, or are you using the version from the Microsoft store? They store their files in different places.

First thing to try is simply exiting out of Firefox and starting it up again. Do you still get the extra toolbar with the error message in the title of the following article: Fix "The bookmarks and history system will not be functional" error message? If you see that bar, Firefox either can't get access to the file -- possibly another process has locked it -- or the file has become corrupted. Before giving up on the file and nuking it (as described in that article), you could try a few other things:

(1) Try to release the file if it's locked

I found a post describing how to use Windows' Resource Monitor to try to figure out what program has opened a "handle" on the file (filter by places): https://superuser.com/a/643312

If it won't release, try a normal shutdown and/or restart of your system. If CCleaner normally runs at startup, see whether you can cancel that or create an exception for Firefox files.

(2) Run the "Verify Integrity" diagnosis and repair function

That's here:

Open Firefox's Troubleshooting Information page using any of these methods:

• "3-bar" menu button > Help > More Troubleshooting Information
• (menu bar) Help > More Troubleshooting Information
• type or paste about:support in the address bar and press Enter

Near the bottom, there is a section titled Places Database -- that's the file which stores history and bookmarks. Click the button labeled Verify Integrity. There may be a 10-15 second delay before results appear.

If all is well, the report that appears below the button should start with:

> Task: checkIntegrity
+ The places.sqlite database is sane
+ The favicons.sqlite database is sane
> Task: checkCoherence
+ The database is coherent
> Task: expire
+ Database cleaned up

et cetera

Does yours say the databases are sane and coherent, or something else? You can select and copy the report, and then paste it into a reply for review and comment.