FastAPI
A Python framework for building web APIs quickly, using standard type hints.
- Stars
- 105k
- Forks
- 10.2k
- Licence
- MIT
- Language
- Python
- Last update
- 4 days ago
- Type
- Library
What it is
FastAPI is a Python framework for building web APIs, the back-end services that apps and websites use to send and receive data. You define your endpoints with standard Python type hints, and FastAPI uses them to validate input and generate interactive API documentation automatically. It is built on Starlette for the web layer and Pydantic for data handling.
- Create a JSON API with path and query parameters validated from type hints
- Serve interactive Swagger UI or ReDoc documentation generated from your code
- Build a REST service that returns predictions from a machine learning model
- Write asynchronous endpoints with async def when your code needs them
Great for
- Python developers building JSON APIs or back-end services
- Teams that want automatic interactive API docs from their code
- ML teams serving model predictions over HTTP, as several cited examples do
- Developers who already use Python type hints and want less boilerplate
Not ideal for
- People who need a full-stack web framework with built-in templates and admin panels, since FastAPI focuses on APIs
- Non-Python teams, because the framework is written for Python
- Beginners with no Python background, since it assumes familiarity with type hints and async concepts
How to get it
- 1
Install with a package manager
You'll need: Python (version not specified in the README excerpt; the badge indicates supported versions) · uv or pip (recommended install tool)
Add FastAPI to a project with uv
uv add "fastapi[standard]" - 2
Run it
- Create a file named main.py with a FastAPI app and a route.
- Start the development server using the FastAPI CLI from the README (the excerpt does not show the exact run command).
- Open the interactive docs in your browser at the local address the server prints.
- 3
Get the most out of it
- Use type hints on parameters so FastAPI validates input and documents it automatically
- Explore the full documentation at fastapi.tiangolo.com for tutorials and deployment guidance
- Consider Typer, a sibling project from the same author, if you need command-line tools instead of web APIs
- Use async def endpoints when your code performs asynchronous I/O
Downloads
Strengths
- Uses standard Python type hints for validation and editor autocompletion
- Generates OpenAPI and JSON Schema documentation automatically
- Released under the permissive MIT license with a large community (over 100k GitHub stars)
Trade-offs
- The README's speed and productivity figures are the authors' own estimates and are not independently verified here
- Scope is limited to APIs, so you will add other libraries for things like templating or database access
- Advanced async behavior requires understanding Python's async model
How it compares
| Project | Stars | Type | Level | Updated | Best for |
|---|---|---|---|---|---|
| fastapi (this) | 105k | Library | beginner | 4 days ago | Python developers building JSON APIs or back-end services |
| redoc | 26k | Library | beginner | 5 days ago | Teams that already write OpenAPI or Swagger specs and want public or internal API docs |
| scalar | 16.4k | App | beginner | 4 days ago | Developers who already maintain an OpenAPI or Swagger document |
| normalizr | 20.8k | Library | intermediate | 4.6 years ago | JavaScript developers who receive deeply nested API responses and want flat, ID-keyed data |
| sanic | 18.6k | Framework | intermediate | 3 months ago | Python developers building web APIs or backend services |
| imgui | 76.9k | Library | intermediate | 6 days ago | Game developers who want an in-engine debug or tools panel |
Stats synced from GitHub. The assessment above was drafted with AI from the project's README on 2026-10-29 and may miss recent changes — check the README before relying on a command. MIT licence: free to use, modify and distribute, including commercially, as long as you keep the copyright notice.