Making ActivityPub Your Social Media Hub for Mastodon and Other Decentralized Services

Making ActivityPub Your Social Media Hub for Mastodon and Other Decentralized Services

For many people who have walked away from Twitter, Mastodon is their first experience with a decentralized social network. There is a lot that can be said about the pros and cons of decentralization, but I want to focus on one very specific technical feature that Mastodon shares with a growing list of other services: ActivityPub.

ActivityPub is a W3C recommended standard published almost five years ago by its Social Web Working Group and defines a decentralized social networking protocol for client applications and servers that connect them. The benefit for users is interoperability between services that accept the protocol.

In practice, this means that users of one ActivityPub service can follow and interact with users of another service, which opens up some interesting possibilities. Tumblr seems to agree. The company plans to add ActivityPub support, so its users can interact with Mastodon’s users. That news piqued my interest in ActivityPub, but I’m not patient enough to wait for Tumblr to add support. Now I wanted to take two ActivityPub services for a spin, so I set up a Pixelfed account on

Pixelfed is sort of a decentralized version of Instagram that has adopted the ActivityPub protocol. Users can post photos, follow other users and send each other messages. The service recently started betaing an iOS app available on TestFlight, so I downloaded it, set up an account, and posted about it on Mastodon.

Because Pixelfed and Mastodon servers are both ActivityPub compliant, anyone can follow my Pixelfed account from Mastodon without creating a Pixelfed account or downloading the app, which is exactly what Federico did:

In practice, it’s even easier to follow someone’s Pixelfed feed. Instead of looking for my username, Federico could have looked up the URL for my Pixelfed profile in a Mastodon app and followed me that way. However, it is worth noting that not all Mastodon applications support the search for non-Mastodon servers. If you’re having trouble adding someone to your Mastodon stream, try Mastodon’s web app, which I’ve tried and know works. Also, be patient as some Pixelfed servers like are struggling with an influx of new users which has hurt its reliability.

As the owner of a Pixelfed account, ActivityPub also offers me some additional benefits. First, I added my Pixelfed account to Ivory, the Tapbots Mastodon app currently in alpha testing. It lets me post photos and respond to followers in the same app I use for Mastodon, which is nice. I also followed my Pixelfed account from my Mastodon account, which allows me to see my posts from my Mastodon feed and promote them to my Mastodon followers, creating the equivalent of cross-posting on two services without having to actually post to both separately.

Although there are a growing number of services that support ActivityPub, including PeerTube, a YouTube video alternative,, which supports parts of the protocol, and many others, it is still early days for the protocol. However, with Twitter reminding users of the danger of relying on a centralized service provider, the pace of ActivityPub adoption is increasing, which should make 2023 a very interesting year for the open web.

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