Property-based fuzzing that generates API tests straight from your OpenAPI schema.
Schemathesis reads an OpenAPI or GraphQL schema and generates thousands of valid and deliberately hostile requests, checking that responses conform to the schema and that the server never returns an unhandled 500. It routinely finds edge cases no hand-written test would cover, for the cost of pointing it at a spec.
Best for
Free tier available
Free tierFree tier: The CLI and Python library are open source and free.
What drives the bill: Open source. A commercial hosted service exists for reporting and continuous runs.
Check current pricing on Schemathesis’s siteFigures are indicative and were last reviewed August 2026. Vendors change pricing often; confirm before you commit.
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