What is a 400 error?

A “400 Bad Request Error” refers to an “HTTP response status code” which indicates that the request could not be processed by the server due to possibly incorrect syntax.

Client side or server side?

The status code 400 in question falls into the category for "client error responses", or error messages that may occur on the end user's side. The 400 status code is often caused by the requester himself. The requester has made a request that the server does not understand and therefore cannot process.

Cause

The cause of a 400 status code can be one of the following:

The requester is trying to send a file that is too large.

The applicant has made a request whose http headers may be incorrect.

The request has changed in some way and is no longer correct.

The applicant has made a request with an incorrect url.

Dissolve

Resolving a 400 status code can sometimes be a bit tricky. In any case, it is useful to check the following things when you get a 400 status code:

When sending files, make sure that the file size does not exceed the specified limit of what is allowed.

Check that the URL/location of the request is correct and does not contain any strange characters.

Empty potentially relevant cookies or caches from the website. It is possible that your internet browser has previously processed the requests and has therefore cached them to speed up the requests in the future. However, this can also cause problems, which can result in a 400 Bad Request. You can read how to clear the cache of your internet browser in the manual How can I clear the browser cache and DNS cache?

If the website or application you use uses any form of authentication, it can sometimes help to log in again.