Choosing an SDK generator: Speakeasy vs Stainless vs Fern vs APIMatic vs OpenAPI Generator

SDK generators, which automatically create language-specific client libraries from API specifications like OpenAPI, are crucial for simplifying API integration and improving developer experience. This detailed comparison of five popular SDK generators—OpenAPI Generator, APIMatic, Fern, Stainless, and Speakeasy—highlights their unique strengths and limitations. OpenAPI Generator is acclaimed for its extensive language support and open-source nature but requires significant maintenance. APIMatic offers an integrated developer portal and affordability but lacks language diversity and runtime type safety. Fern, backed by Postman, integrates SDK and documentation generation but uses a custom DSL, posing compatibility challenges. Stainless, favored by AI companies like OpenAI, provides robust features but relies on a custom configuration layer. Speakeasy, recommended for its balance of quality, features, and flexibility, emphasizes runtime type safety, minimal dependencies, and OpenAPI fidelity, catering to enterprises needing comprehensive language support and adaptable deployment options.