OpenAPI

Vendor-neutral specification for describing HTTP APIs in a language-agnostic format. Provides a consistent way to document REST endpoints, request and response schemas, authentication, and metadata throughout the API lifecycle. Specifications are typically written in YAML or JSON, enabling tooling to generate clients, servers, documentation, and tests from a single source of truth.

The OpenAPI Specification is maintained by the OpenAPI Initiative under the Linux Foundation and is the most widely adopted API description standard. A large ecosystem of parsers, code generators, mock servers, and documentation tools accept OpenAPI as input, giving teams flexibility in vendor selection and avoiding lock-in. Compared to alternatives like RAML or API Blueprint, OpenAPI has the broadest tool support and cross-team familiarity.

Key capabilities:

• JSON and YAML formats for defining paths, operations, parameters, schemas, and security
• Code generation for server stubs and client SDKs across many languages
• Interactive documentation and mock servers derived from the spec
• Contract testing and validation against the defined schema
• API gateway and infrastructure configuration from a single document

Teams use OpenAPI for API-first design, where the spec is drafted before implementation, and for code-first workflows where annotations or runtime introspection produce the spec from existing code. It underpins developer portals, CI/CD validation pipelines, and integration with API management platforms.