[JackC]

For anyone looking to mess around with making a single file ActivityPub server, this looks like a good intro to the spec: https://socialhub.activitypub.rocks/t/guide-for-new-activity...

That page also links to https://blog.joinmastodon.org/2018/06/how-to-implement-a-bas..., which is a demo of hardcoding one part of the spec from scratch.