After a Firefox account sync on a new machine, I was left with many duplicate bookmarks. This extension removed them, and then the empty folders they had been in, with just a few clicks. It took just a few moments. This was a great time saver.

Quickly handled 12,000 duplicate bookmarks caused by bugs in Xmarks

Highly recommended!

Probably the best extension to remove duplicates at present.

I had over 1322 duplicate bookmarks because of a syncornisation error and this simple addon did the job in less than a minute.
Simple design, easy to use and a top recommendation !

really helpful

Awesome and fast UI for selecting duplicates in one go, and just one click to delete... Really appreciate that only bookmark editing permissions were required! Suggested improvement: deletion process is slow with lots of disk usage (read/writes). Perhaps add option to process the deletion entirely in RAM?

Very simple, easy and straight to the point!

How do I open it?! In "Details" it says "click the extension symbol (duplicate stars) or use the link in the options page" but that just opens "Details" again! And there is no "Options" option.
(Yes, this is a Firefox issue so I'm going 5* for now, in hope.)
Edit: OK so 8h later & I still haven't found the "ON" switch!
This is crazy!
1* then.
(Not "3 years ago" but 22 Oct 2021!)
Edit2: NOW I see the icon in the Menu bar & it works! Back to 5*. For now at least. (I KNEW it was Firefox!)