Articles/HTTP

HTTP 431 Request Header Fields Too Large — What It Means

What HTTP status code 431 Request Header Fields Too Large means, when servers return it, and how to handle it correctly.

Published September 26, 2026

HTTP 431 Request Header Fields Too Large — The request headers are too large for the server to process.

Key points

  • Caused by an individual header, or the combined size of all headers, being too large
  • Commonly triggered by an oversized cookie or an authentication token stored in a header
  • Resolved by trimming cookie size or moving large data out of headers
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