431 Request Header Fields Too Large

When a client sends a HTTP request with HTTP headers that are too big, a server can use 431 Request Headers Fields Too Large in response.

This response can be used if either the total size of all headers exceeded some limit, or if there are individual headers that are too big.

If a client sees a 431, it could hypothetically remove some headers and try again. The most obvious candidate for this could be removing cookies.


HTTP/1.1 431 Request Headers Too Large
Content-Type text/html

<h1>Too many cookies! Try to reduce your cookie footprint.</h1>


HTTP series

This article is part of a series about the HTTP protocol. Read them all here:

Informational 1xx

Successful 2xx

Redirection 3xx

Client Error 4xx

Server Error 5xx

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