I used xmarks for a very long time. Since it was shutdown I never really found suitable replacement. It was great because it had plugins for all the main browsers I used. This meant that my bookmarks followed me everywhere.
I was looking for a replacement, and I wanted a self hosted solution since I didn't want to rely on a 3rd party service for something very important to me. I also didn't want to install and maintain a heavy database like mysql, postgres on my meager VM. It also needed to be browser agnostic. Surprisingly there are not that many options out there that met this simple criteria.
I found Shaarli which brands itself as The personal, minimalist, super-fast, database free, bookmarking service. It makes use of nodejs and php. Its is self hosted and has no support for a database and relies on no 3rd party services. It also has browser plugins for Firefox, Chrome, Android, and IOS.
The install process was pretty nice as it would check all the dependencies and permissions. I was able to get it installed on my Centos 7 box was ease. I will say that the default interface is kind of ugly, and it lacks the ability to have a tree view. That being said it very much relies on tags and maybe if you can remember how to navigate the tree, you can remember the tags also. It also has plugins to extend the app. Soon I will start migrating all my bookmarks over to it.
Another neat feature is that you can have public and private plugins. The private bookmarks are password protected and the atom feed is aware if you are logged in or not. Since this is personal there is only one account. There is even an API!
I would encourage you to check it out.