Bad Request 400
Reference guide
Request path
- You (reached)
- DNS (reached)
- Cloudflare edge (reached)
- Origin (answered with a warning)
400
Likely cause
The origin/application rejected this request as malformed.
What to do
- Check. Check your application's access/error logs for the exact request that returned 400, including its headers and cookies — an oversized cookie or header set is a common cause.
- Fix. Correct or reduce the offending request data (e.g. clear oversized cookies, fix malformed query parameters or request bodies) at the source generating the request.
- Verify. Retry the same request and confirm it now returns a normal response.