Bluesky - Documentation

What it is¶

Bluesky is a Twitter/X-like public social app — the flagship, reference application built on the [[at-protocol|AT Protocol]], run by Bluesky PBC (a public benefit corporation). The same relationship holds here as between Mastodon and ActivityPub: atproto is the protocol, Bluesky is one application on it, and Bluesky PBC has made product decisions — character limits, its specific feed defaults, its specific moderation service — that aren't mandated by the protocol itself and that a different atproto app could do differently.

Unlike Mastodon within the fediverse, though, Bluesky is currently the dominant atproto app by a wide margin, and — as covered in the [[at-protocol]] guide — it also runs the one full-network relay most of the ecosystem depends on, so the protocol/app distinction matters less in practice for Bluesky than it does for Mastodon/ActivityPub, at least for now.

Growth and positioning¶

Bluesky's user base grew roughly 60% in 2025 and sits around 44 million accounts as of early 2026, positioning it as the most visible mainstream alternative to X to emerge from the post-2022-Twitter-acquisition wave of decentralized social experiments — ahead of Mastodon in raw account numbers, if not in the total size of the ActivityPub-speaking fediverse across all its apps combined.

What makes the product distinctive¶

These are Bluesky-the-app features, each one a direct expression of something atproto's architecture makes possible (see [[at-protocol]] for the underlying mechanics):

Custom feeds: rather than one company-controlled algorithm, feeds are built by anyone as independent services reading the firehose, and any user can subscribe to any feed instead of (or pinned alongside) the defaults. A feed can be a simple keyword/hashtag filter or a full custom ranking algorithm.
Starter packs: a shareable bundle of up to 150 accounts and up to 3 custom feeds, used to onboard a new user directly into a curated community rather than dropping them into an empty timeline. Sharing one auto-follows the bundled accounts and feeds for whoever signs up through it.
Labelers and composable moderation: users individually choose which labeling services to subscribe to, with a per-label choice of Off/Warn/Hide, on top of Bluesky's own baseline moderation labelers. Separately, mute lists (silently hide someone, they're not notified) and block lists (fully sever interaction both ways, visible publicly) give finer-grained personal control than most centralized platforms expose.
Custom domain handles: instead of you.bsky.social, you can use any domain you control as your handle (you.yourdomain.com) via the same DNS-verification mechanism atproto identity resolution uses generally — free, and it signals you're not dependent on Bluesky's own hosting for your identity.
Account portability: move your account to a different PDS — including a self-hosted one — without losing your handle, followers, or history, a direct payoff of atproto's DID-based identity model.
No ads, at least as of this writing — a positioning choice, not a protocol constraint.

Where Bluesky sits relative to X/Threads¶

	Bluesky	X (Twitter)	Threads
Ownership model	Decentralized (atproto)	Centralized	Centralized
Account portability	Yes	No	No
Custom feeds	Unlimited, user/community-built	Limited presets	Algorithm-driven only
Moderation	Composable labelers, user-selectable	Centralized	Centralized
Advertisements	None	Yes	Yes

Governance and centralization caveats¶

Bluesky PBC is a for-profit public benefit corporation, not a nonprofit foundation — a real governance difference from Mastodon gGmbH or the Matrix.org Foundation, even though the underlying protocol is open and other companies/individuals can build competing apps on it. And as covered in the [[at-protocol]] guide, the fact that Bluesky currently operates the only full-network relay that matters is a genuine, protocol-acknowledged centralization point: the architecture doesn't require this, but the current reality concentrates a meaningful amount of infrastructure control in one company regardless.

Interoperating with the rest of the fediverse¶

Bluesky doesn't natively speak ActivityPub, but Bridgy Fed bridges the two networks: an opt-in service that translates profiles, posts, likes, follows, and replies between Bluesky/atproto and Mastodon/ActivityPub, letting users on either side follow and interact with users on the other without leaving their home app. It's a translation layer sitting outside both protocols rather than a change to either one.

Strengths and weaknesses¶

Strengths: fast-growing, polished mainstream-friendly product; genuinely portable identity; strong, user-controlled moderation tooling (labelers, mute/block lists); custom feeds meaningfully change the discovery experience versus a single fixed algorithm.

Weaknesses: for-profit corporate governance (unlike the nonprofit models behind Mastodon and Matrix); the one-relay-that-matters centralization point; younger ecosystem with faster protocol churn than the fediverse's more settled ActivityPub tooling.