ActivityPub is the technical standard enabling communication between decentralized social networks. Created in 2018 by the World Wide Web Consortium (W3C), it forms the backbone of the Fediverse—a federation of independent platforms that share content without a central authority. This protocol allows services like Mastodon to interconnect directly.

The system uses two core components: an Inbox and Outbox, accessible via standard HTTP/HTTPS APIs. Privacy is maintained through the WebFinger protocol for locating these endpoints. While designed for social media, ActivityPub's architecture supports diverse applications, including content management systems and collaborative development tools.

With over 20 million users and full W3C backing, ActivityPub offers a mature alternative to corporate-controlled platforms. Its built-in moderation features address a common pain point in decentralized systems. By remaining open-source and community-maintained, it presents a viable path toward more resilient, user-controlled social networking infrastructure.