Bookmarks Clean Up - Find and remove duplicated bookmarks manually and in batches, get rid of broken bookmark links and empty folders.
Raindrop.io - All your articles, photos, video & content from web & apps in one place.
Fast Bookmark Scanner II - Scan your bookmarks in order to delete duplicated links empty folders or merge duplicated folders.
Firefox Sync - Bring your Firefox bookmarks, tabs, or passwords wherever you go with Firefox Sync. Share between computers and mobile devices. Get Firefox now!
EverSync - Everhelper - Eversync
syncmarx - A simple Web Extension for synchronizing bookmarks between browsers.