The Arsse was designed from the start as a server for multiple synchronization protocols which clients can make use of. Currently the following protocols are supported:

The protocols are merely different ways of accessing and manipulating the same data: subscribing to a newsfeed using one protocol will see the newsfeed also present when later connecting via another protocol, for example. Because not all protocols work according to the same concepts, however, sometimes the interactions between them are not obvious. These interactions are documented here when warranted.