Bookmark Duplicate Detector is a cool firefox addon which lets you find out duplicate bookmarks among all your firefox bookmarks. It also lets you delete all those duplicate bookmarks so, that you can get rid of all the duplicate bookmarks forever.
This is the best extension which lets you find and delete all the duplicates bookmarks one by one. If you have lot of bookmarks this extension is the best to remove duplicates bookmarks easily.
Bookmark Duplicate Detector also lets you search bookmarks with names, description or keywords. It can really save hell amount of time if you have a large number of bookmarks.