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When SmartBear acquired Swagger, they donated the specification language to the newly formed OpenAPI Initiative, and officially renamed the Swagger specification to the OpenAPI 2.0 Specification. But they retained the Swagger brand name to refer to their commercial and open source tools that work with the OpenAPI specification.

So Swagger-UI, Swagger-Core, Swagger-Codegen, etc., are still active projects on GitHub that are aligned with the OpenAPI Specification, but are maintained separately, on their own release schedules.  

The OAI Technical Steering Committee has continued evolving the specification, publishing the  OpenAPI 3.0 Specification in 2017. RepreZen also joined the OpenAPI Initiative in 2017. Work on the specification is ongoing, with incremental updates and new features under active development.

Swagger and the OpenAPI 2.0 Format

Before the Swagger specification was renamed as the OpenAPI 2.0 Specification, the term "Swagger spec" was widely used to refer to a document describing an API in a JSON or YAML format, conforming to the Swagger 2.0 specification.  

Today, many users still use the terms "Swagger" to refer to the OpenAPI 2.0 Specification format, and "Swagger spec" to refer to an API description document in this format. RepreZen API Studio uses these terms in some parts of the UI, but refers to OpenAPI 3.0 and later versions as "OpenAPI."  

Glossary of Terms

OpenAPI Document

  • A document that describes an API, using a JSON or YAML format that conforms to the OpenAPI Specification.

OpenAPI Initiative (OAI)

  • An industry consortium formed under the Linux Foundation

OpenAPI Specification (OAS)

  • An industry-standard language for describing REST APIs.  Used most often to refer to OpenAPI 3.0 or later.


  • A brand name trademark owned by SmartBear, used in its open source and commercial software that works with the OpenAPI Specification.
  • May be used informally to refer to the OpenAPI 2.0 Specification, formerly known as the Swagger specification.

Swagger Spec

  • Informally refers to an OpenAPI 2.0 API description document in YAML or JSON format.

Swagger UI

  • A cool way to show API documentation with a built-in “Try it out” button.