>The idea of an open web where actors use common standards to communicate is as old as, well, the web. "The dreams of the 90s are alive in the Fediverse," Lemmer-Webber told me.
>
>In the late '00s, there were more than enough siloed, incompatible networking and sharing systems like Boxee, Flickr, Brightkite, Last.fm, Flux, Ma.gnolia, Windows Live, Foursquare, Facebook, and many others we loved, hated, forgot about, or wish we could forget about. Various independent efforts to standardize interoperation across silos generally coalesced into the Activity Streams v1 standard.
>
>Both the original Activity Streams standard, and the current W3C Activity Streams 2.0 standard used by Mastodon and friends, offer a grammar for expressing things a user might do, like "create a post" or "like👍 a post with a given ID" or "request to befriend a certain user." The vocabulary one would use with this grammar is split into its own sub-standard, the Activity Vocabulary.
>
>Now that we have a way to express a person's stream of thought and action in JSON blobs, where do all these streams go? The ActivityPub standard is an actor-based model which specifies that servers should have a profile for each actor providing a universal resource indicator (URI) for each actor's inbox and outbox. Actors can send a GET request to their own inbox to see what the actors they follow have been posting, or they can GET another actor's outbox to see what that specific actor has been posting. A POST request to a friend's inbox places a message there; a POST request to the user's own outbox posts messages for all (with the right permissions). The standard specifies that these various in- and outboxes hold activities in sequential order, much like our familiar social media timelines.
>
>...
>
>Here we have the vision of the Fediverse: a set of ActivityPub nodes, scattered across the globe, all speaking a common language. Mastodon is one of many efforts to implement the inboxes and outboxes of the ActivityPub standard. There are dozens of others, ranging from other microblogging platforms ("It's like Mastodon, but...") to an ActivityPub server that runs a chess club.
>
>In theory, they all intercommunicate; in practice, not so much. The sources of incompatibility stem from several issues, from imperfections in the standard to questions of how online communities should form to efforts to reach beyond the standard post/comment/follow format of typical social networks. > >... > >What's next? The Fediverse may remain a host of small hosts. But there are economies of scale. In the federation model, a small, ragtag community sharing an instance is now stuck paying the server bill. > >In terms of skill and time costs, the preparation for many of the systems on the Fediverse is as easy as "just spin up a Docker container on a Raspberry Pi." Of course, most people cannot understand and execute that (relatively) simple instruction. > >Or the Fediverse may centralize. Large instances can be bought. The CEO of Tumblr has promised to implement ActivityPub ASAP, and with 135 million monthly active users, that could make Tumblr the bright giant around which the rest of the Fediverse revolves. MacWright speculates that in such a case, “Inevitably everyone's gonna get grumpy that they're dominating the standard and it's no longer an Indieweb thing, and the cycle starts over.”

Moving (back) to a set of open standards with an aim for interoperability is fundamentally a good direction to be moving in. Walled gardens certainly bring their users a certain set of benefits, but if recent actions by various platforms have shown, also brings a set of challenges as well. It will be interesting to see what the future brings for ActivityPub and its various platforms, and hopefully this growth is managed well, with an eye to longevity and resiliency.