What is openauth?

OpenAuth is an open-source authentication server that you host yourself. Authentication is the system that handles logging in: it checks who someone is and issues a token that proves their identity to the rest of your application. Most developers either build this themselves inside their app or pay for a service like Auth0 or Clerk to handle it. OpenAuth is a third option: a complete, self-hosted server that handles the login process centrally for all of your apps at once. Because it follows the OAuth 2.0 standard, any application that can work with OAuth can use it, including web apps, mobile apps, internal admin tools, and third-party clients. It supports multiple login methods through a concept called providers. You can enable login with GitHub or Google, or use built-in flows like email and password or a PIN code sent by email. You can also enable "login with your app" flows so external developers can use your platform as an identity source. One deliberate design choice is that OpenAuth does not handle user management, meaning it does not store a database of users or their profile data. Instead, when someone successfully logs in, OpenAuth calls a function you write, giving you the chance to look up or create the user in your own database. This keeps the tool focused and avoids imposing a specific database structure on you. The server can be deployed to AWS Lambda, Cloudflare Workers, or a standard Node.js or Bun environment. It needs only a minimal key-value store for data it must keep, such as refresh tokens, and there are ready-made adapters for Cloudflare KV and DynamoDB. A prebuilt, themeable login UI is included so you can have a working login page immediately without designing one yourself. OpenAuth is built by the team behind SST, a tool for managing cloud infrastructure, and SST provides ready-made components for deploying OpenAuth to AWS or Cloudflare with minimal configuration.