Playing with ActivityPub

This article is the detailed, technical overview of Mastodon I was looking for.

What I built isn’t an ActivityPub system as much as a Mastodon-compatible one. I think this is the key contradiction of the ActivityPub system: it’s a specification broad enough to encompass many different services, but ends up being too general to be useful by itself.

The contrast of ActivityPub to RSS is pretty stark. Read this and, damn, you gotta love RSS!

• You can implement an RSS feed with basically any system. A static site generated by a static site generator like Jekyll? Sure! You can even write an RSS feed by hand and upload it with FTP if you want.
• Your RSS feed doesn’t know who’s reading it. If you have 1 million people subscribed, sure, that’s fine. At most you’ll need to use caching or a CDN to help the server serve those requests, but they’re just GET requests, the simplest possible kind of internet.
• RSS has obvious points of optimization. If 10,000 people subscribe to my RSS feed but 5,000 of them are using Feedbin, those 5,000 can share the same GET request that Feedbin makes to pull the latest posts.
• An RSS feed reader only needs a list of feed URLs and an XML parser. It doesn’t need to have its own domain name or identity in the system. A feed reader can be a command-line script or a desktop application.