OpenAPI

OpenAPI is an open standard for describing HTTP APIs in a format that both people and machines can read. The OpenAPI Initiative, a project under the Linux Foundation, maintains the specification.

An OpenAPI document lists the paths, operations, parameters and responses of an API. Tools read that file to produce documentation, generate client code, create tests and check design rules. Because the format is shared, teams can use many different tools with the same description.

• Describe endpoints, parameters and responses
• Generate client code and server stubs from one file
• Share a common format across many tools
• Published specification versions on the project site
• Source and specification hosted on GitHub

API designers, backend developers and documentation teams who want a common way to describe APIs. Tool vendors also build on the standard so their products can work together.

The specification is free to use, and the repository is licensed under Apache 2.0. The project is run by a technical steering committee and offers membership and events. A good description still takes care to write, because tools are only as useful as the file they read.