The Python web framework designed for building APIs with type hints and automatic OpenAPI generation is FastAPI.
FastAPI uses standard Python type annotations to validate incoming data, convert values to the expected types, and describe request and response structures. Those declarations feed an OpenAPI schema automatically, which in turn powers interactive documentation such as Swagger UI and ReDoc.
The framework was created by Sebastián Ramírez and is built around Starlette for web handling and Pydantic for data validation and schema generation. Because it supports ASGI, it is well suited to asynchronous endpoints and modern high-performance Python services.
A common mix-up is choosing Flask or Django simply because they are more established. Flask is a lightweight general web framework, while Django is a broad, batteries-included web framework. FastAPI’s defining combination is API-focused design, type-driven validation, and standards-based documentation.