A popup showing all duplicate bookmarks will be opened. After a confirmation your duplicate bookmarks will be removed and the amount of removed duplicates will be presented.
Note: Bookmark Deduplicator will sequently read the addresses of every bookmark and mark each one that points to the same address as a previously checked one for deletion. Consequently, the bookmarks that have been checked first - usually higher up in the folder hierarchy - will not be affected.
With a huge amount of bookmarks, the browser may appear frozen while the extension is at work, this is no sign of an error - simply wait for or continue the finalization of the cleanup process.
Please make sure to create a backup of your bookmarks before using a removal tool! Also, carefully read the above description of the current extensions features. An extended version with customization options will be provided at some time in the future.