What is this?

One of the great, defining characteristics of the Fediverse is that it is on numerous, autonomous servers that all work together. You can follow other users on other servers — but sharing links to profiles and posts can be tedious. You can view the content on the origin server, but you need to be on the server hosting your account to boost, favorite, or follow.

Much like how the mailto: link opens your preferred email application to let you email anyone, fedv.link links are designed to easily open ActivityPub posts and profiles in the end user's preferred server.

How do I use this?

https://fedv.link/<activity pub url>

As above, just prepend your ActivityPub link with https://fedv.link/. We'll do the rest.
Note - this has only been tested with Mastodon instances. Threads.net does not always work, yet.

Do I need to sign up?

Nope. This all works within your browser. Set your preferred server, and then all fedv.link links will open on that site.

For the more technical audience: All logic on this site is client-side JavaScript. Your server is stored in localStorage.