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!)

Saved me hours of sorting after the xmarks sync bug that duplicated countless bookmarks.

Thank you!

Does exactly what it says on the tin, very simple but extensible.

Simple & very useful. Particularly the regex/expert mode really helps (even with the prefab settings). The rather thorough description and the dev's responses show that he knows what he's doing (as can be expected from an experienced academic mathematician).
All the best to Mr. Väth.

Works fast and accurate