OpenAPI Specification (OAS)
The OpenAPI Specification (formerly Swagger) is the dominant industry standard for describing HTTP-based RESTful APIs. OAS describes endpoints, operations, parameters, request/response schemas, authentication, and examples in a machine- and human-readable format. The active versions are 3.0.x and 3.1.0 (which is fully aligned with JSON Schema 2020-12). OpenAPI is governed by the OpenAPI Initiative, a Linux Foundation project, under the Apache 2.0 license.