fastapi

modern Python web framework CLI

TLDR

Run development server

$ fastapi dev [main.py]

Run with specific host and port

$ fastapi dev [main.py] --host [0.0.0.0] --port [8080]

Run production server

$ fastapi run [main.py]

Run with auto-reload disabled

$ fastapi dev [main.py] --no-reload

Specify the app location

$ fastapi dev [main.py:app]

SYNOPSIS

fastapi command [options] path

fastapi is the CLI for FastAPI, a modern Python web framework for building APIs. It wraps Uvicorn ASGI server for convenient development and deployment.
fastapi dev starts a development server with auto-reload—code changes trigger automatic restart. Use for local development with --host 0.0.0.0 to allow external access.
fastapi run starts a production-oriented server without auto-reload and binding to all interfaces. For actual production, consider Uvicorn or Gunicorn directly with more configuration options.
The path argument points to a Python file containing a FastAPI instance. Use path:variable syntax to specify a non-default app variable name.
FastAPI generates automatic API documentation at /docs (Swagger UI) and /redoc endpoints based on your route definitions and type hints.

PARAMETERS

--host address

Bind address. Default: 127.0.0.1 (dev), 0.0.0.0 (run).

--port port

Server port. Default: 8000.

--reload

Enable auto-reload (dev default).

--no-reload

Disable auto-reload.

--workers count

Number of worker processes.

--root-path path

ASGI root path for proxied setups.

--app name

Application variable name. Default: app.

--proxy-headers

Trust X-Forwarded headers.

--help

Display help information.

COMMANDS

dev path

Start development server with auto-reload.

run path

Start production server.

CAVEATS

The CLI is a convenience wrapper; production deployments often use Uvicorn/Gunicorn directly for more control. Auto-reload may miss some file changes. Debug mode exposes detailed error pages.

HISTORY

FastAPI was created by Sebastián Ramírez and first released in December 2018. Built on Starlette and Pydantic, it emphasizes type hints for validation, serialization, and documentation. The framework quickly became one of the most popular Python web frameworks for APIs. The fastapi CLI was added later to simplify the development experience. FastAPI is used in production by Microsoft, Netflix, Uber, and many others.