Super, ce module, il fait exactement ce que j'attendais. Plusieurs choix sont possibles pour marquer automatiquement les doublons (Dups) ou alors à la main.

Unpretentious and practical. When it finds duplicates it asks which to select (newest or oldest entry).

Amazing extension!
Due to constant import/export from/to other browsers I had a total of 15k bookmarks.
This extension removed the dupes with a single click to 3k bookmarks within minutes.
Highly recommended.

Seems like there is a bug regarding capital vs non-capitalized folder names. After running the "Moved marked bookmarks to 'Dupes'" command, any of my folders with a non-capitalized name were left without any bookmarks in them. The non-capitalized folders were empty.



EDIT: User error, the plugin is working as intended!

Super! (and amazing that Firefox doesn't have this essential functionality buit-in!)

The best in its kind.

Just removed duplicate bookmarks using this add-on..
Thanks

Great nifty tool. Very fast and accurate.
Need to understand the options once we run the Bookmarks DUPES.
Options to mark the duplicates in many ways.
For a huge volume of bookmark duplicates use one of the intuitive 'marking' options.
(Example in each duplicate group, select all but latest).
We can also manually choose and remove but when faced with a huge volume better to leverage the tool.
It also creates a "Dupes' folder we can move (similar to Recycle Bin on a computer) before permanently removing or choose to directly remove. As the Add-on warns, once removed there is no way to get back. But that is how it works. (It is like when we empty recycle bin)

Awesome tool. Kudos to the creator (s)

Solved +1000 dups problem pretty easily and without issue. Thanks so much!
Update 2 yrs later: with Martin's quidance, changed those unreadable pink Visited Links to deep red in Fx:
Settings/General/Colors/Manage Colors/Visited Links. I am happy!

THANK YOU MARTIN! GREAT WORK!
I had over 50k bookmarks to deal with.
Bookmark Dupes did 99% of the work for me!