Missing Host Header in Requests

Missing Host header

$ python -c "import requests; requests.get('http://127.0.0.1:8000', headers={'Host': ''})"
Traceback (most recent call last):
  ...
requests.exceptions.HTTPError: 400 Bad Request: Missing Host header

Why this happens

HTTP/1.1 requires a Host header. Overriding it incorrectly or using proxies/misconfigured DNS can cause servers to reject the request.

Fix

Don’t override the Host header unless necessary. Let Requests set it automatically based on the URL. If using proxies, ensure they don’t strip/modify Host.

Wrong code

import requests
requests.get('http://api.local', headers={'Host': ''})

Fixed code

import requests
requests.get('http://api.local', timeout=10)  # no manual Host header