Xmarks Sync has stopped working. All my bookmarks have disappeared. I’m trying to install the add-on again from my.xmarks.com, but Firefox displays “This add-on is not compatible with your version of Firefox” and “Not compatible with Firefox Quantum”. Firefox Add-ons Finder does not find Xmarks among the available add-ons. I am using Firefox Quantum. OS is WIN 10 x 64, version 1709. Please help
I would recommend switching to Bookmark OS. I moved from Xmarks a while ago and have never looked back
Perhaps this link can help you:
Be warned, though: due to restrictions of WebExtensions API, Xmarks is no longer capable of preserving/syncing bookmarks tags.
Post a support ticket to Xmarks in case you need more details.
Many users are complaining for the Xmarks problems these days. I’ve been a heavy Xmarks user for years (I have about 5000 bookmarks) and I’m looking for a valid alternative. But it seems there aren’t good around. So the only solution I’ve found for now is Bookmarks OS. It does not have sync features but at least it’s reliable (I hope).
Another alternative is the built-in Firefox Sync feature. It works well, only has limitations that it’s only for Firefox, does not have share features, it lacks a web page for the bookmarks and has some problems if you have thousands of bookmarks (as I have).