OpenAPI Generator
A Java tool that reads an OpenAPI spec (2.0 or 3.x) and generates API client libraries, server stubs, documentation, and config files from it — 50+ client generators and 40+ server generators across the language map openapi-generator-docs. Apache-2.0, ~26.5k stars, 7.6k forks, latest release v7.23.0 (2026-06-08) openapi-generator-docs. Maintained by OpenAPI Tools, which the README is careful to note is not affiliated with the OpenAPI Initiative that owns the spec itself.
The pitch, in the post that routed here: “You should not have to rebuild the same API client for every language.”
What it generates
Far past SDKs. Clients for roughly 50 languages/frameworks (Java has ~15 HTTP-client variants alone; C++ includes Arduino and Unreal Engine 4; the list runs to Elm, Eiffel, OCaml, XoJo, Zapier). Server stubs for ASP.NET Core, Spring, FastAPI, Flask, Gin, Servant, Rails, and more. Docs as HTML, Confluence Wiki, Asciidoc, Markdown, PlantUML. And a long tail that shows the real ambition: GraphQL, JMeter, MySQL Schema, Postman Collection, Protocol Buffer, WSDL openapi-generator-docs. That tail matters — once the spec is the source of truth, it can project into a database schema or a load test just as readily as into a client, which is the schema-driven-codegen argument in one table.
Runs as a Maven or Gradle plugin, a CLI (Homebrew, Docker, npm), or a hosted service — so it can sit either in the build (repo-wide, reproducible) or in a developer’s hands (one-shot, drifting). Templates are Mustache, which is what makes the generator set extensible by contributors rather than by the core team openapi-generator-docs.
Where it came from
A 2018 community fork of Swagger Codegen, taken between versions 2.3.1 and 2.4.0 and pitched as a drop-in replacement openapi-generator-docs; the repo dates to 2018-05-12 openapi-generator-docs. Set that against this spoke’s other sources: TypeScript is Microsoft’s, yaff Yandex’s, lore Epic’s — big-tech infrastructure released outward. OpenAPI Generator is the opposite, a contributor body that walked away from a vendor-controlled project and funds itself through Open Collective and company sponsorships. Same layer of the stack, an entirely different way of being paid for.
Caveat
The README warns that if the spec, templates, or options come from an untrusted source, you should review them before generating — otherwise it’s code injection openapi-generator-docs. A codegen tool executes its inputs by definition, so the spec is not inert data; it’s a program.
Related
openapi-generator-post · openapi-generator-docs · schema-driven-codegen · openapi-tools · clickhouse-rowbinary · developer-tooling · dart · kotlin