Guessing what went wrong here is not an easy task. The server throws a 400 Bad Request error when the request becomes defective somehow. The HTTP internet protocol has not been attached correctly which is why it cannot be processed.
The server interprets such a request as faulty or harmful and prevents the website from displaying itself. Every time it is not necessary that the browser will mention the root cause of what the problem is while communication happens between a server and a client. It just shows ‘HTTP 400 Bad Request’.
We can point out more details from the status code if the target web server uses IIS 7.0, IIS 7.5 or IIS 8.0. This is not necessary that while browsing through the internet this error will occur. Other programs can also receive this status code while communicating with the server. It can happen. This 400 error can come even if your file that you are trying to upload is of large size or even if the header becomes too long. Some web servers set an upper limit for the header length.
Cause of error 400
There are numerous reasons that can cause this error. Listed below are the most probable:
- The client might have sent a faulty request. Web servers look for headers to process the request and verify that the client is not trying to attempt anything malicious.
- The client might be uploading a file that is too large. Most of the servers have an upper limit set for the size of the file client’s upload.
- The client is trying to access an invalid URL. If such a case happens the server throws a 400 Bad Request Error.
- The client is using an expired or an invalid cookie. Sometimes it is possible that a browser identifies a local cookie is a session cookie. If this cookie matches the session token from another request and from a different client then the server sends error 400.
- The DNS cache might consist of an invalid IP address. The server throws error 400 in such a scenario.
How to fix error 400
- The most common reason for error 400 is an incorrect URL. URLs are case sensitive so be very careful while typing out a URL.
- Always check for unacceptable special characters in the URL.
- Clear local cookies. You can clear them manually or can clear all of them at once.
- When uploading a file be cautious about its size. Most websites mention the maximum size of a file for uploading it. Look out for it.
- If the website needs some authentication and you have already cleared the cookies. Try logging out and then logging in.
- If you upgraded your system or installed some new plugin right before the error 400, try roll backing to the last stable version.