PawPub has a simple but flexible extension system, allowing additional features to be added to the protocol while preserving compatibility with other software that may not support them. Each extension is identified by a unique URI, which may or may not resolve to anything, although it's recommended to place documentation for the extension there. Extensions can either exist as extra properties attached to objects such as actors, notes, interactions or in instance metadata, or as stand-alone extension objects.

On this wiki, you can find a few “semi-official” extensions (which are generally recommended for use over any equivalent third-party extensions, but are still not part of the PawPub core protocol itself):

• Pages (not final)
• Poke (not final)
• Link Previews