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HTTP_STATUS_REQUEST_HEADER_TOO_LARGE
The code is not standardized. Oversized cookies, long authorization tokens, many forwarding headers, or generated tracing headers are common causes. Other servers may return 400 or 431 for the same underlying condition.
Measure the complete request header size and review NGINX header-buffer settings together with application cookie policy. Raising limits should be deliberate because it increases per-connection memory use.
NGINX large client header buffers
Operational meaning of HTTP 494 for HTTP_STATUS_REQUEST_HEADER_TOO_LARGE
HTTP 494 (HTTP_STATUS_REQUEST_HEADER_TOO_LARGE) is a client-error response. AllStat records its meaning as “494 Request header too large”. For HTTP_STATUS_REQUEST_HEADER_TOO_LARGE, interpret it with the request method, selected representation, response headers, and the specification or product that defines the code; the number alone does not prove that application work completed.
Client and server handling for HTTP_STATUS_REQUEST_HEADER_TOO_LARGE
- Treat HTTP_STATUS_REQUEST_HEADER_TOO_LARGE as a condition visible at the request boundary; inspect authentication, syntax, preconditions, routing, and resource state before retrying.
- For HTTP_STATUS_REQUEST_HEADER_TOO_LARGE, preserve the response body and challenge or retry-related headers because they often carry the actionable reason.
- For HTTP_STATUS_REQUEST_HEADER_TOO_LARGE, automatic retry is safe only when the method and status contract allow it and the request has been corrected.
For telemetry, record HTTP 494, method, authority, route template rather than secrets, response headers relevant to caching or retry, latency, upstream identity, and whether the response originated at the application or an intermediary.
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