Leywn is the last demo backend you will ever need. Whether you are building a new API client, stress-testing a retry strategy, demonstrating an integration, or just need a quick echo server for a workshop — Leywn has you covered with a single docker run.

Every endpoint is purposefully designed: mirror your requests with /echo, simulate network latency with /delay, stream chunked responses with /stream, test all your auth flows, generate random data, hash and encode payloads, and more. Zero dependencies to manage, zero state to worry about, and everything tunable via LEYWN_ environment variables.

Need a REST API with data behind it? Drop a JSON file into a folder under /mocks and Leywn serves it as a full CRUD API — with its own generated OpenAPI, linked below.