Protocol divergence dictates social choice

Technical architecture differences

Bluesky uses the AT Protocol to manage social interaction, while Mastodon and Threads rely on the ActivityPub protocol. This technical split forces teams to choose between two different federation models. The AT Protocol employs a microservice architecture that separates identity, hosting, and reach into distinct services such as Personal Data Servers, relays, and AppViews to facilitate modular and diverse user experiences. Users store data in Personal Data Servers, while relays aggregate content into a network-wide data stream called the firehose. Clients communicate with these services through an HTTP API called XRPC, using JSON for data and CBOR for authenticated information. This model differs from ActivityPub, where a single host server manages both user data and the application.

Identity involves a dual system. This system combines a mutable handle, like a domain name, with an immutable decentralized identifier. The handle system provides verification through a domain name or a text file on a web service. Bluesky reached 46 million total registered users by August 2026. The network remains centralized in some aspects because relays act as indispensable components in the design.

Moderation and user control

Moderation workflows vary by platform. Users are accountable to their specific instance in Mastodon’s host-centered system, and administrators can defederate from other servers to block content. This can disrupt communication if an administrator cuts ties with a specific server. Bluesky uses a stackable moderation model. The model includes network takedowns, labels from moderation services, and user-controlled mutes or blocks. In 2025, the platform reported 309,000 accounts used domain handle verification and 4,327 accounts received formal verification badges.

Personal Data Servers (PDSes) host user repositories and media. They facilitate repository updates, backups, and data queries. The AT Protocol prioritizes data portability, so users can migrate repositories without data loss, even if a PDS becomes adversarial. You should recognize that the AT Protocol design allows users to move between services without losing their posts or follows.

Bridging these two protocols remains difficult. Bluesky lacks native cross-posting or seamless follows between its network and the ActivityPub ecosystem. The only bridge, Bridgy Fed, requires users to opt-in manually.

The 2026 landscape

The 2026 Bluesky roadmap introduces custom feeds for sports and elections, along with real-time tools and "LIVE" badges. The platform also provides drafts and supports videos longer than three minutes. These updates attempt to provide a more polished experience than the community-driven models. The "Atmosphere" ecosystem grows through third-party app integrations and profile plugins. Specialized nodes for video, like Streamplace, provide new ways to consume content.

Threads remains a massive presence. Meta’s platform has ten times the users of the Fediverse and Bluesky combined. Threads users can opt-in to share content with the Fediverse, but they cannot see replies or likes from Mastodon accounts. This one-way sharing highlights the power imbalance between centralized platforms and decentralized protocols. Mastodon reached 9.1 million registered users at the end of 2024, yet Bluesky reached 42 million users by February 2026. Can these smaller networks survive if the major platforms continue to prioritize proprietary distribution?

The decision between these platforms involves a trade-off between community control and feature polish. Mastodon provides autonomy through instance-level governance, while Bluesky delivers a modular, app-centric experience. The gap between the two networks remains wide.