FastAPI

FastAPI is a modern Python web framework designed specifically for building APIs with automatic documentation generation and request validation based on Python type hints. By annotating function parameters with standard Python types and Pydantic models, FastAPI automatically validates incoming data, serializes responses, and generates interactive OpenAPI documentation accessible through Swagger UI and ReDoc.

Performance is a core design goal. FastAPI is built on Starlette for the web layer and Pydantic for data validation, using async/await syntax to handle concurrent requests efficiently. Benchmarks consistently place it among the fastest Python frameworks, approaching the performance of Node.js and Go for I/O-bound workloads, making it suitable for production APIs serving high traffic.

For web development, FastAPI has rapidly become the preferred choice for new Python API projects. Its type hint-based approach means the same code that defines the API also documents and validates it, eliminating documentation drift. The automatic OpenAPI spec generation is valuable because frontend developers can use it to generate typed API clients. FastAPI works well as the backend for React, Vue, or Next.js frontends, with dependency injection for managing database connections and shared logic.