431 Request Header Fields Too Large

Meaning

Client error responses indicate a problem with the request.

Causes

• Request or response flow is affected by the status meaning.
• Headers or request body may require changes.

How to fix

• Validate request parameters and authentication.
• Fix client-side input or URL and retry.

Example

HTTP/1.1 431 Request Header Fields Too Large

Official references

IANA HTTP Status Code RegistryOfficialRegistryhttps://www.iana.org/assignments/http-status-codesOpen in new tab MDN HTTP response status codesReferenceDocshttps://developer.mozilla.org/en-US/docs/Web/HTTP/StatusOpen in new tab RFC 9110 (HTTP Semantics)ReferenceSpechttps://www.rfc-editor.org/rfc/rfc9110Open in new tab RFC 9110: 431 status codeReferenceSpechttps://www.rfc-editor.org/rfc/rfc9110Open in new tab

FAQ

• Is this my problem or the server’s? — It depends on the status class (4xx vs 5xx).
• What should I check first? — Start with the request URL, headers, and body.

When to contact support

If it persists, contact the service owner.