OpenAPI is a specification that defines a standard, programming-language-agnostic interface for building and documenting RESTful APIs. Formerly known as Swagger, OpenAPI allows developers to describe the structure of their APIs in a standardized format, typically using JSON or YAML. This enables both humans and machines to understand and interact with the API.

One of the key benefits of OpenAPI is its ability to automate many parts of the API lifecycle. For example, developers can generate API client libraries, server stubs, and testing tools directly from the OpenAPI specification. This reduces the time spent on repetitive tasks and ensures consistency across different environments.

OpenAPI also promotes collaboration between teams by making API documentation more accessible and understandable. The documentation can be rendered as interactive API documentation, allowing developers to experiment with API endpoints in real-time. Tools like Swagger UI and Postman leverage OpenAPI specifications to create user-friendly API testing interfaces.

By standardizing API documentation and development, OpenAPI enhances interoperability, making it easier for organizations to integrate services and collaborate across different platforms.