ValueError: Invalid JSON provided to requests

7 Dec 2025

1 min read

Invalid JSON when sending

$ python -c "import requests, json; requests.post('https://example.com', data='{"a":1,}', headers={'Content-Type':'application/json'})"
Traceback (most recent call last):
  ...
ValueError: Invalid JSON

Why this happens

Malformed JSON string or wrong usage of data vs json argument.

Fix

Use json= with Python dicts or validate JSON strings.

Wrong code

import requests
requests.post('https://example.com', data='{"a":1,}', headers={'Content-Type': 'application/json'})

Fixed code

import requests
payload = {"a": 1}
resp = requests.post('https://example.com', json=payload)
print(resp.request.body)