head to head · open source
openapi-generator vs hey-api
openapi-generator has 26,748 GitHub stars, 7,675 forks, 5,751 open issues and last shipped yesterday. hey-api has 5,417 stars, 434 forks, 630 open issues and last shipped 25 days ago. openapi-generator leads on adoption by 394% (26,748 vs 5,417 stars). openapi-generator is written in Java under Apache-2.0; hey-api is written in TypeScript under MIT. openapi-generator has attracted 29% as many forks as stars, hey-api 8%. openapi-generator was the more recently maintained of the two, and both are self-hostable with no licence fee. The two share 2 topic tags (api-client, openapi), so they are genuine substitutes rather than adjacent tools.
Two open source projects, one decision. Both are free and self-hostable — the differences are community size, license terms, language stack and release pace.
← all 13541 open source comparisons
Side by side
| openapi-generator | hey-api | |
|---|---|---|
| GitHub stars | ★ 27K | ★ 5.4K |
| License | Apache-2.0 | MIT |
| Written in | Java | TypeScript |
| Last push | 2026-09-17 | 2026-08-24 |
| Forks | ⑂ 7.7K | ⑂ 434 |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick openapi-generator if
- You weight community size — 27K stars and counting
- You want the Apache-2.0 license terms
- Your stack matches Java
- You value the larger contributor base for long-term maintenance
pick hey-api if
- You want the hey-api feature set and don't need the biggest community
- You prefer the MIT license terms
- Your stack matches TypeScript
- You evaluated both and hey-api fits your workflow better
About openapi-generator
OpenAPI Generator is an Apache 2.0 licensed Java tool that generates API client libraries, server stubs, documentation, and configuration automatically from an OpenAPI Specification, and it is built for development teams that keep a machine readable API description and want generated code to stay in step with it.
read the full openapi-generator overview →
About hey-api
Hey API is an open source ecosystem for turning API specifications into production ready code. It is distributed as a monorepo containing all of the project's open source packages, with the two primary generators being openapi ts for TypeScript and openapi python for Python. The TypeScript generator ships with more than twenty plugins covering SDKs, Zod schemas, and TanStack Query hooks, while the Python generator produces SDKs and Pydantic models. A supporting library, spec types , provides TypeScript definitions for OpenAPI and JSON Schema specifications with complete inline documentation. The project lives in …
read the full hey-api overview →
More in Developer Tools
Related comparisons
More API Development & Testing projects
Compare either of these against the rest of the API Development & Testing field.
Frequently asked questions
Is openapi-generator or hey-api more popular?
openapi-generator has 26,748 GitHub stars and hey-api has 5,417. openapi-generator has the larger community by that measure.
Are openapi-generator and hey-api free?
Both are open source. openapi-generator is licensed under Apache-2.0 and hey-api under MIT. Neither carries a licence fee.
What is the difference between openapi-generator and hey-api?
openapi-generator is written in Java and hey-api in TypeScript. The practical differences are community size, licence terms, language stack and release cadence — all compared in the table above.
Which should I choose, openapi-generator or hey-api?
Choose openapi-generator if you want the larger community (26,748 stars) or its Apache-2.0 licence terms. Choose hey-api if its feature set, stack or MIT licence fits better. Both are self-hostable.