ymarks
The official ymarks browser extension.
What is ymarks?
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Summary
ymarks is a free and open source add-on for several modern web browsers, licensed under the terms of the CDDL, with a server component written in C that allows you to synchronize your browser's bookmarks with an SQLite3 database that can be hosted either on your local machine or somewhere in your intranet (or even the internet). It is supposed to be a single-user system in order to reduce complexity and increase privacy, but you can (technically) run as many parallel instances of ymarks as you like.
Safety
Risk impact
ymarks may not be safe to use and it requires some risky permissions. Exercise caution when installing this extension. Review carefully before installing.
Risk likelihood
ymarks is probably trust-worthy. Prefer other publishers if available. Exercise caution when installing this extension.
Screenshots
Similar extensions
Here are some Chrome extensions that are similar to ymarks: