Solve the 400 Bad Request Bad Request when logging in to the WordPress background

If you are logged inWordPress backend400 Bad Request, what should I do?

400 Bad Request
Your browser sent a request that this server could not understand.
Size of a request header field exceeds server limit.

• 400 Bad Request
• Your browser sent a request that this server does not understand.
• The size of the request header field exceeds the server limit.

What should I do if I get a 400 Bad Request when logging in to the WordPress backend?

Some netizens said that switching to php 7.2 on the VPS server, all plugins and themes are (and are) as usual and updated.

Not sure if this is due to the php version, but now I get a 400 error message like this:

"Bad Request
Your browser sent a request this server That Could not understand.
Size of a request header field exceeds server limit."

This only happens when logged in with Chrome and clicking links to articles and categories.

How to solve it?Is the problem caused by php 7.2?

How to fix 400 Bad Request when logging into WordPress backend?

You might be surprised, but most 400 errors in WordPress can be fixed by clearing your browser's cache and cookies.

Browser cache temporarily stores images, scripts and other parts of websites you visit to speed up your browsing experience.Some of the data stored may be out of date, thus resulting in a 400 Bad Request Error.Clearing your browser cache and cookies may resolve the 400 HTTP error code.

Clear your browser cache and cookies

In Chrome, enter this address in the browser's URL field:chrome://settings/clearBrowserData

You'll have direct access to a clear browsing data dashboard.

1. Here, make sure the "Cached images and files" and "cookies" boxes are checked.
2. Then click the Clear Data button.
3. Refresh your page, if it still doesn't work, go to the next step!

If the browser cache and cookies still cannot fix the problem, please try the following solutions:

The error "Size of request header field exceeds server limit" section explains the problem.

When you click a link, too much information is passed to your hosting server, which places a limit on the amount of information it is willing to accept.

• You'll need to contact your web hosting provider's support to see if they can raise that limit?
• Or do you need to ask the developer to investigate further to see what created the information that caused the limit to be reached?