ymarks is a two-component KISS bookmark synchronization service, it consists of a server component which you'll have to run anywhere and a client component which will have to be installed in your browser(s). Its name is a pun on the (now defunct) Xmarks service.
Which browsers are supported?
By the time of writing, ymarks semi-officially supports Mozilla Firefox and Vivaldi. Rumors suggest that Google Chrome, Opera and Microsoft Edge might or might not work as well.