status Registered
Verified 2026-09-18 · registry updated
2025-09-15HTTP 431 Request Header Fields Too Large
The request headers are too large for the server to process.
Use 431 when cookies or custom headers exceed configured limits.
httpstatus coderequest headerslimits
Response (http)
HTTP/1.1 431 Request Header Fields Too Large
Use 431 when cookies or custom headers exceed configured limits.
Common mistakes
- Trying to fix 431 with body-size limits; the problem is the request headers, often large cookies.
Registry reference: rfc6585