ActivityBot is a full ActivityPub server in a single PHP file. Upload two files to a web host and you have a Fediverse bot — no containers, no package imports, no framework ceremony. It supports media uploads, private messages, threads, following, content warnings, and most standard Mastodon-style features.

The code is fully commented as a teaching tool for how ActivityPub actually works. Handmade in London. Source: gitlab.com/edent/activity-bot. NLnet page: ActivityBot.

Running even a small presence on the Fediverse usually means a full server stack. That pushes bots and experiments back onto centralised APIs (Twitter/X, Instagram) that can revoke access overnight. ActivityBot makes a standards-based actor cheap enough to host on ordinary PHP hosting, so automated and educational accounts need not depend on a vendor SDK.