Elysia

Elysia is a TypeScript web framework built for the Bun runtime. Its schemas act as the single source of truth for validation, type inference and API documentation.

You define routes with a schema for the body, params and responses. Elysia checks incoming data against that schema, normalises it, and gives your handler the correct types at runtime and at compile time. Handlers can return strings, JSON, files or streams, and the framework also supports WebSockets for live data.

• Schemas that drive validation and types
• File, JSON and stream responses
• Built-in WebSocket support
• OpenAPI documentation generated from schemas

TypeScript backend teams and API developers who use Bun and want strong typing without writing types twice. It suits services where input validation and documentation need to stay in step with the code.

Elysia is open source under the MIT licence and free to use. It is designed for Bun, so check compatibility before running it on Node.js or another runtime. The docs describe the framework's benchmarks, but results depend on the workload you test.