What Is HTTP 431 Request Header Fields Too Large?

HTTP 431 Request Header Fields Too Large explained, and what it means when you see it in CI/CD and deployments.

HTTP 431 means the server refuses the request because its header fields are too large.

What it means

A 431 happens when headers (often a huge cookie or a long Authorization token) exceed the server limit.

When you see it in CI/CD

In CI, a 431 can come from oversized auth tokens or accumulated cookies. Trim headers or use a smaller token.

Key takeaways

• 431 means headers too large.
• Often an oversized token/cookie.
• Trim the headers.

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