Lemmy uses the ActivityPub protocol (a W3C standard) to enable federation between different servers (often called instances). This is very similar to the way email works. For example, if you use gmail.com, then you can't just send mails to other gmail.com users, but also to yahoo.com, yandex.ru and so on. Email uses the SMTP protocol to achieve this, so you can think of ActivityPub as "SMTP for social media". The amount of different actions possible on social media (post, comment, like, share, etc) means that ActivityPub is much more complicated than SMTP.
Lemmy uses the ActivityPub protocol (a W3C standard) to enable federation between different servers (often called instances). This is very similar to the way email works. For example, if you use gmail.com, then you can not only send mails to other gmail.com users, but also to yahoo.com, yandex.ru and so on. Email uses the SMTP protocol to achieve this, so you can think of ActivityPub as "SMTP for social media". The amount of different actions possible on social media (post, comment, like, share, etc) means that ActivityPub is much more complicated than SMTP.
As with email, ActivityPub federation happens only between servers. So if you are registered on `enterprise.lemmy.ml`, you only connect to the API of `enterprise.lemmy.ml`, while the server takes care of sending and receiving data from other instances (eg `voyager.lemmy.ml`). The great advantage of this approach is that the average user doesn't have to do anything to use federation. In fact if you are using Lemmy, you are likely already using it. One way to confirm is by going to a community or user profile. If you are on `enterprise.lemmy.ml` and you see a user like `@nutomic@voyager.lemmy.ml`, or a community like `!main@ds9.lemmy.ml`, then those are federated, meaning they use a different instance from yours.
Felix Ableitner
4 years ago