When you find an interesting website, TrishTech.com for instance, you add it to your bookmarks list so that you can visit it later easily without having to look for it. In Firefox, bookmarking of websites can be done either by pressing the hotkey Ctrl + D or by right-clicking over a page and selecting Bookmark this page. But sometimes we bookmark a website more than once, without realizing it. This results in having the same website bookmarked under different categories multiple times. If you want to remove the duplicate bookmark entries, then you can can make use of the Bookmarks Deduplicator plugin for Firefox.
You can visit the Mozilla Firefox addons website to download and install the Bookmarks Deduplicator extension for Mozilla Firefox. The extension does not require for you to restart the browser. Once the extension is installed, you can go to the Firefox Addons Manager, by pressing the hotkey Ctrl + Shift + A. Click on the Options button next to the Bookmarks Deduplicator extension.
This would open the Bookmarks Deduplicator extension options in your Firefox browser. This extension does not have any options to speak of. But it has a Start button in the options. If you click on this Start button then it would go through all your bookmarks and see if you have any duplicated bookmarks.
If it does not find any duplicate entries, then it will show you a message that no duplicate bookmarks were found. But if it finds any duplicate bookmarks, then it would show you a list of all the duplicates found. Upon confirmation, the duplicate bookmarks will be removed and you will be shown the number of duplicate bookmarks removed.
Although the latest version of Firefox is designed in such a way as to prevent you from bookmarking the same page twice, but if you somehow succeed in bookmarking one website multiple times, then the Bookmarks Deduplicator can help you remove the extra copies of the same bookmark. Removing the duplicates not only removes your confusion but also makes it easy for Firefox to load the bookmarks list each time you start it.
You can download Bookmarks Deduplicator extension from https://addons.mozilla.org/.