OpenAPI Generator
The most widely adopted open-source code generator forked from Swagger Codegen. Given an OpenAPI spec, generates API client SDKs, server stubs, and documentation for 50+ languages and frameworks. 26k+ GitHub stars, 600k weekly NPM downloads, and 30M Docker pulls.
Swagger / OpenAPI
Swagger UI is the canonical open-source renderer for interactive API documentation from OpenAPI specs, with 28k+ GitHub stars. SwaggerHub adds collaborative API design, versioning, and governance at scale. The de facto standard for REST API specification across the industry.