What is HTTP Status 431?
Sometimes when you're developing or using a web application, you may encounter the error HTTP 431 Request Header Fields Too Large. This error indicates that one or more HTTP request headers (such as cookies and other metadata) are too large for the server to process. In fact, the server cannot handle requests with header sizes exceeding its limitations.
Why does this error occur?
One of the most common reasons for this error is the use of very large cookies or a large number of cookies. For example, if your site stores a lot of data in cookies, you might soon face this error. Additionally, other factors such as improper usage of headers or using plugins that add extra headers can also lead to this problem.
How can this issue be resolved?
To resolve this error, you should initially limit your request headers. Try to ensure that no data is stored excessively in headers or that they are minimized. Another simple way is to reduce the number and size of cookies. In some cases, you can adjust server settings to accept larger sizes, but this should be done cautiously and with specific goals in mind.
Example of a header size adjustment code in Nginx server
http {
server {
large_client_header_buffers 4 16k;
}
}
Explanation of the code line by line
http {This block is used to define general HTTP server settings in Nginx.
server {This block defines settings for a specific server configured within the HTTP block.
large_client_header_buffers 4 16k;This line specifies the number and size of header buffers that can hold larger client headers. The number 4 means four buffers, and 16k is the size of each buffer in kilobytes.
}Ends the server block.
}Ends the HTTP block.
Keep in mind that any changes in server settings should be done carefully and with full awareness of the situation. Increasing header sizes may have security implications.