Bluesky (social network)
Bluesky is a decentralized microblogging social platform and a Public Benefit Corporation (PBC). It is built on the AT Protocol (Authenticated Transfer Protocol), an open-source standard for distributed social applications. Bluesky distinguishes itself from centralized platforms like X (formerly Twitter) and federated alternatives like Mastodon through its focus on account portability, algorithmic choice, and a "big world" aggregation model. [1]
History
Bluesky began in 2019 as an internal project at Twitter, initiated by then-CEO Jack Dorsey with the goal of creating a decentralized standard for social media. In 2021, it spun off as an independent company under the leadership of CEO Jay Graber.
Following Elon Musk's acquisition of Twitter in 2022, Bluesky completely severed its ties with the company. It launched an invite-only beta app in 2023, which saw waves of growth often correlated with controversial changes at X. On February 6, 2024, Bluesky opened to the public, removing the waitlist and releasing new federation and moderation tools. [2]
Technology (AT Protocol)
Bluesky is the flagship reference application for the AT Protocol. The protocol is designed around three core pillars aimed at ensuring user agency and global scale.
- Identity (DIDs): Users are identified by persistent Decentralized Identifiers (DIDs). A user's handle (e.g.,
@alice.bsky.social) is merely a domain name that resolves to their DID. This allows users to use any domain they own as their handle and retain their identity even if they change hosting providers. - Data Repositories (PDS): User data (posts, likes, follows) resides in signed "repositories" hosted on Personal Data Servers (PDS). This design enables "credible exit": a user can move their PDS to a new host without losing their history or social graph. [3]
- Aggregation (Relays and AppViews): The protocol uses "Relays" to crawl PDS instances and aggregate content into a global "Firehose." "AppViews" then consume this firehose to build the application state (feeds, notifications). This creates a cohesive, global view of the network.
Comparison with other models
The AT Protocol's architecture differs significantly from other federated protocols, such as ActivityPub (used by Mastodon).
| Feature | AT Protocol (Bluesky) | ActivityPub (Mastodon) |
|---|---|---|
| Model | Aggregation ("Big World"): Content is pulled from Personal Data Servers (PDS) into a global "Firehose" relay. | Federation ("Small World"): Servers send messages to each other's inboxes (like email). |
| Identity | Portable: Identity (DID) is separate from hosting. Users can switch servers without losing their social graph. | Server-Bound: Identity is tied to a specific server (e.g., @user@instance.social). Moving requires migration tools. |
| Data Storage | Signed Repositories: User data lives in a cryptographically signed repository on a PDS. | Server Database: User data resides in the local database of their home instance. |
Unlike ActivityPub servers which federate by sending messages to each other, AT Protocol's reliance on Relays and AppViews creates a more web-like global view compared to the server-siloed view of Mastodon. [4]
Key Features
- Algorithmic Choice: Bluesky does not force a single central algorithm on users. Instead, it offers a marketplace of custom feeds created by third-party developers (e.g., "Science," "Cat Photos," "Mutuals Only"). Users can subscribe to and pin these feeds to their home screen. [1]
- Composable Moderation: Moderation is "stackable." In addition to the platform's baseline safety rules, users can subscribe to external "Labelers"—services that tag content or accounts (e.g., a "Spider-hater" labeler that hides spider photos). This allows communities to self-govern and set their own standards without imposing them on the entire network. [2]
Analysis and Critique
- Decentralization Concerns: Critics argue that Bluesky's reliance on a massive "Firehose" of data makes true decentralization difficult. Aggregating the entire network's traffic requires significant storage and bandwidth (estimated at 5TB+ for a relay in late 2024), effectively limiting full participation to well-resourced entities and potentially recreating "Big Tech" centralization. [5]
- Corporate Control: While the protocol is open, the Bluesky company currently retains significant influence. It operates the main relay, the default AppView, and the
did:plcdirectory (the default identity method). Furthermore, Direct Messages (DMs) are currently routed through the company's servers without end-to-end encryption. [5] - "Credible Exit": Proponents argue that AT Protocol prioritizes "credible exit"—the ability for a user to leave a platform with their data and audience intact—over the strict server-equality model of ActivityPub. [4]
Governance
Bluesky is organized as a Public Benefit Corporation (PBC). This legal structure requires the company to balance stockholder interests with its specific public benefit mission: to develop and drive the adoption of technologies for open and decentralized public conversation. The company was initially funded by Twitter but has since raised independent venture capital. [1]
- ^a ^b ^c Bluesky. Company - Bluesky. Bluesky. https://bsky.social/about/faq.
- ^a ^b Perez, Sarah. Bluesky is now open for anyone to join. TechCrunch. https://techcrunch.com/2024/02/06/bluesky-is-now-open-for-anyone-to-join/.
- ^ Bluesky. Protocol Overview - AT Protocol. Bluesky. https://atproto.com/guides/overview.
- ^a ^b Berjon, Robin. ActivityPub Over ATProto. Robin Berjon. https://berjon.com/ap-at/.
- ^a ^b Lemmer-Webber, Christine. How decentralized is Bluesky really? Dustycloud Brainstorms. https://dustycloud.org/blog/how-decentralized-is-bluesky/.