Bluesky is an open social network built on the AT Protocol. Users can choose between feeds and custom algorithms, set moderation lists and content filters, and use one account across multiple apps. The AT Protocol consists of Personal Data Servers (PDS) that host user data, relays that aggregate updates, and AppViews that provide network-wide features. Accounts have a permanent identity (DID), so a user can move to another PDS. Bluesky is available as a web app and mobile apps.
Bluesky is operated by Bluesky Social, PBC, a US public benefit corporation. Its privacy policy says personal data may be processed and stored anywhere in the world, without naming a hosting location; a representative in Ireland is designated for the EEA. The app's source code is MIT-licensed, and a PDS can be self-hosted, for example on a server in the EU. A self-hosted PDS gives control over where your own data is stored, but the network-wide services remain shared.