---
set: 4
code: 431
title: Request Header Fields Too Large
---
The 431 status code indicates that the server is unwilling to process the
request because its header fields are too large. The request MAY be resubmitted
after reducing the size of the request header fields.
It can be used both when the set of request header fields in total is too large,
and when a single header field is at fault. In the latter case, the response
representation SHOULD specify which header field was too large.
For example:
```
HTTP/1.1 431 Request Header Fields Too Large
Content-Type: text/html
Request Header Fields Too Large
Request Header Fields Too Large
The "Example" header was too large.
```
Responses with the 431 status code MUST NOT be stored by a cache.
Source: [RFC6585 Section 5][1]
[1]: