What is a 400 error?

Error 400, commonly referred to as “Bad Request,” is an HTTP response code that indicates that the server was unable to process the request sent by the client due to incorrect syntax. This means that the request was malformed, so the server was unable to understand or process it.

Common terminologies associated with this error:

  • Bad Request
  • HTTP 400
  • 400 Bad Request
  • HTTP Error 400
  • Invalid Request

What causes a 400 error?

Error 400 can be caused by a variety of issues, including:

  • Malformed URLs: The requested URL may have incorrect syntax or contain invalid characters.
  • Request size too large: The request may exceed the size the server is able to handle.
  • URL Length Limitations: Some servers limit the length of URLs they can accept.
  • Corrupted Cookies: If the client sends cookies that the server cannot interpret.
  • Malformed Request Headers: If the headers sent in the request are poorly formatted or contain invalid information.
  • Malformed POST requests: In some cases, the body of the POST request may be incorrectly formatted or contain invalid data.

What are the effects of a 400 error?

When a 400 error occurs, the end user typically receives an error message indicating that their request could not be processed. Effects include:

  • The temporary or permanent inaccessibility of a specific resource or web page.
  • Frustration for the user, especially if he does not understand the cause of the error.
  • For website owners, this can lead to decreased user confidence and potentially a drop in traffic if the error affects a substantial portion of the site.

Fix a 400 error

If you are a visitor to the site:

  • Check the URL: Make sure it is correctly formatted and does not contain any strange or invalid characters.
  • Clear your cookies: Some cookies may be corrupted or no longer valid, causing the error.
  • Reduce request size: If you are sending data, make sure it does not exceed acceptable limits.

If you are the owner or administrator of the site:

  • Check the server logs: They may provide clues as to what caused the error.
  • Check server configuration: Make sure limits on request size, URL length, etc. are configured correctly.
  • Update your code: If the error is caused by some form of query or data that you didn't anticipate, you may need to update your code to handle it.
  • Provide clear error messages: Make sure users receive useful information when an error occurs, to help them understand and resolve the problem.

It is always beneficial for website owners to use monitoring and debugging tools to quickly detect such errors and take corrective actions.

Here are some other error codes:

  • Error 401
  • Error 403
  • Error 405
  • Error 503
  • Error 522