HTTP 494 Request Header Too Large
Updated Free mock REST & WebSocket APIs
HTTP 494 Request Header Too Large — nginx's internal code for a request header or cookie that exceeds its buffer size.
- Class
- 4xx Client Error
- Defined in
- Unofficial (nginx)
- Official
- No — nginx-specific
- Cacheable by default
- No (unless Cache-Control/Expires say so)
- Safe to retry
- Not without changing the request
Try it: get a real 494 response
Our test endpoint answers every request with 494 Request Header Too Large.
curl -i https://mockfox.dev/api/status/494Use it in tests, health-check monitors or to see how your client handles a 494. Add ?delay=2000 to slow it down.
What does HTTP 494 mean?
nginx logs 494 when a request line or header doesn't fit large_client_header_buffers (default 4 × 8k), but the client receives a 400 page titled "Request Header Or Cookie Too Large". Clear the site's cookies, or raise the limit with large_client_header_buffers 4 32k;.
How to fix 494
- Visitors: Reload the page, check the address for typos, and clear the site's cookies. If it persists, the site owner needs to fix it.
- Developers: Read the response body and server logs for details, fix the request (method, headers, body, credentials) and return a clear error message to clients.
Example 494 response
HTTP/1.1 400 Bad Request Server: nginx Content-Type: text/html # (logged internally as 494)
4xx Client Error: The request contains an error or can't be fulfilled — fix the request before retrying. See the full list of HTTP status codes.
Related status codes
- 431 Request Header Fields Too LargeThe server refuses the request because a header — or all headers together — is too large.
- 400 Bad RequestThe server can't process the request because it's malformed or invalid.
- 413 Content Too LargeThe request body is larger than the server is willing to accept.
Related tools
Frequently asked questions
What does HTTP 494 Request Header Too Large mean?
nginx's internal code for a request header or cookie that exceeds its buffer size.
Is 494 a client or a server error?
494 is a 4xx code, so it signals a problem with the request (as seen by the server). Retrying the identical request usually gives the same result.
Is 494 an official HTTP status code?
No. It isn't in the IANA HTTP Status Code Registry; it's specific to nginx. Generic HTTP clients treat it as an unknown 4xx status.
How can I test how my app handles a 494?
Call https://mockfox.dev/api/status/494 — it responds with 494 to any method, with CORS enabled. Add ?delay=2000 to simulate a slow response.