Cookies & Headers in Python
From the FastAPI cheat sheet · Cookie & Header Parameters · verified Jul 2026
Cookies & Headers
Extract cookie values and HTTP headers from requests.
python
from fastapi import Cookie, Header
@app.get("/items/")
async def read_items(
session_id: str | None = Cookie(default=None),
user_agent: str | None = Header(default=None),
):
return {"session": session_id, "agent": user_agent}💡 Header names are auto-converted: X-Request-Id becomes x_request_id in Python
⚡ Use Response.set_cookie() to send cookies back to the client
📌 Always set httponly=True on session cookies to prevent XSS access
🟢 Use list[str] for headers that can appear multiple times (e.g., X-Token)
cookiesheadersparameters