HTTP Status Codes
HTTP 431 Request Header Fields Too Large
431 Request Header Fields Too Large
The server is unwilling to process the request because the request header fields are too large, either individually or in total.
Error AtlasError Documentation and ResolutionObserved message
431 Request Header Fields Too Large
Why it happens
- The request includes excessively large cookies or authentication tokens.
- Too many custom headers or forwarded headers are being attached to the request.
- An intermediary or application is repeatedly appending to headers across redirects or retries.
How to fix it
- Reduce cookie size and remove unnecessary cookie values where possible.
- Trim oversized or duplicate headers from the client or proxy configuration.
- Check whether redirects, middleware, or proxies are inflating headers unexpectedly.
Official reference
MDN: 431 Request Header Fields Too LargeRelated errors
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