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What is OpenAPI (Swagger)?
Definition
OpenAPI (formerly Swagger) is a specification for describing REST APIs. It defines endpoints, parameters, request/response schemas, authentication methods, and error codes in a machine-readable format (YAML or JSON).
Why It Matters
OpenAPI specifications auto-generate API documentation (Swagger UI), client SDKs, server stubs, and test suites. They serve as the single source of truth for API contracts between frontend and backend teams.