Why this page exists¶
[[mastodon]] is, by a wide margin, the fediverse's most-deployed application — but [[activitypub|ActivityPub]] was always designed to federate kinds of applications, not just microblogging. Each app below is independently developed, independently governed, and makes its own product decisions on top of the same shared protocol, exactly the way Mastodon does — meaning a user on any one of them can follow, like, reply to, or boost content from any other, including Mastodon, without leaving their home app.
Pixelfed — photo sharing¶
Pixelfed is the closest fediverse analog to Instagram: image-first posts, albums, stories-style ephemeral content, and a grid profile layout. It federates the same way Mastodon does — every post, like, and follow is an ActivityPub activity delivered to followers' inboxes — so a Mastodon user can follow a Pixelfed account directly and see their photo posts appear in their normal timeline (typically rendered as an image with a caption, since Mastodon has no native "photo app" UI of its own). Pixelfed instances are self-hosted the same way Mastodon ones are, with the same tradeoffs: independent moderation policy per instance, and identity tied to whichever instance you've registered on.
PeerTube — video hosting¶
PeerTube, developed by the French nonprofit Framasoft, is a YouTube-style video platform built on ActivityPub plus WebTorrent/P2P for actual video delivery — a meaningful technical difference from the other apps here, since federation handles the metadata and social graph (likes, comments, subscriptions, the video's existence) while playback can be assisted peer-to-peer across viewers to reduce any single instance's bandwidth burden. A Mastodon user following a PeerTube channel sees new uploads show up as ordinary posts with an embedded video link and thumbnail; richer PeerTube-specific features (playlists, channel subscriptions beyond a simple follow) generally don't translate across the protocol boundary the same way.
Lemmy and Mbin — link aggregation and forums¶
Lemmy and Mbin (a fork of the earlier Kbin project) are Reddit-style link-aggregation and discussion platforms: communities ("magazines" in Mbin's terminology), threaded comments, upvotes/downvotes. These apps stretch ActivityPub further than microblogging or media sharing does, since a "community" with its own moderators and a vote count is a somewhat different shape than a single actor's inbox/outbox — but it still federates on the same underlying activity types, and a community hosted on one Lemmy instance is joinable and postable-to from any other Lemmy or Mbin instance, same as following works elsewhere in the fediverse.
WriteFreely — long-form blogging¶
WriteFreely is a minimalist, Medium-style federated blogging platform — deliberately plain, with no built-in social features beyond what federation itself provides (follows, likes, replies arriving from the rest of the fediverse on your posts). It's also one of the services Meta has explicitly named as a Threads federation target (see [[threads]]), making it one of the more concrete small-scale beneficiaries of that larger platform's partial ActivityPub adoption.
Funkwhale — audio and music¶
Funkwhale applies the same federated model to audio: music libraries, podcasts, and audio uploads, federated so that a Funkwhale user on one instance can discover and play back media another instance is hosting, and follow/favorite activity propagates the normal ActivityPub way.
Owncast — live streaming¶
Owncast is a self-hosted live-streaming server (a Twitch alternative) with ActivityPub support for the social layer around a stream — followers get notified when a streamer goes live, and chat/follow activity can federate out to the wider fediverse, while the actual video stream itself is served directly from the streamer's own instance rather than through ActivityPub.
What's shared versus what's app-specific¶
Every app on this page inherits the same structural tradeoffs covered in the [[activitypub]] guide: identity tied to whichever instance you registered on, moderation handled per-instance plus defederation as the blunt network-level tool, and loosely-typed JSON-LD meaning that cross-implementation rendering of app-specific features (a Lemmy vote count, a PeerTube playlist, a Pixelfed story) is often degraded or absent when viewed from a different kind of app, even though the core follow/like/reply/boost vocabulary works uniformly everywhere.