400 Error Codes: Identify and Fix Bad Request Errors

HTTP status codes are a critical part of how the Internet functions. They serve as responses from a server when a client makes a request. However, what happens once you get an HTTP status code indicating an error? In this article, learn what the HTTP status codes are and how to understand and resolve the HTTP Bad Request 400 error code.

What are HTTP status codes?

HTTP status codes are the codes issued by a server when a client makes a request to the server, such as when you visit a website. There are five standard classes of status codes:

  • 1XX informational response, which means request received
  • 2XX successful request, which means request understood and accepted
  • 3XX redirection, which means further action is required to complete a request
  • 4XX client error, which means the request cannot be completed
  • 5XX server error, which means the server failed to fill a valid request
A 400 error code, indicating a bad request

Client error codes

400 error

HTTP error 400 means the client made a bad request. Error 400 Bad Requests can be caused by:

  • Malformed request syntax
  • Invalid request message framing
  • Deceptive request routing

If you get a 400 error code, check that you entered the URL correctly or that the link you clicked contains the correct URL.

401 error

HTTP error 401 means the user lacks the proper authorization to access the target resource. In other words, the request could not be authenticated. The 401 error code can occur if the client fails to provide proper authentication to the server they are trying to access or if the server banned the client.

If you receive a 401 error code you think was made by mistake, check the URL to make sure you entered it correctly. If the URL is correct, try flushing the DNS, clearing browser cookies, or logging out and then logging back in.

However, if none of these work, it could be the case that the website’s server is down. In this case, try contacting the webmaster of the website.

403 error

HTTP error 403 means the client is forbidden from completing the request. For example, the user might not have the necessary permissions or the user may be attempting a prohibited action. 403 error codes are similar to 401 codes, but with a 403 forbidden error, re-authenticating makes no difference.

If you receive a 403 error code and do not feel the site correctly denied you access, contact the webmaster of the website to request access. In rare cases, the code could result from an error on your end. With any error code, it’s always worth a shot to check the URL, refresh the page, and clear your cookies and cache.

404 error

HTTP error 404 means the requested resource could not be found. 404 Page Not Found errors are one of the most common errors on the Internet. They occur when you successfully communicate with the server, but the server cannot find the requested resource.

For example, a dead link can cause a 404 error. This happens often because web administrators frequently update pages without updating corresponding links elsewhere on the Internet.

As with other errors, if you receive a 404 error code, try the following:

  • Refresh the page
  • Check the URL
  • Delete cache and cookies
  • Browse the website or use a search engine to find the page you’re looking for
  • Contact the webmaster of the website

Server error code

500 error

HTTP error 500 is an internal server error message that’s provided when an unexpected error occurs and no specific reason for the error can be found. Because 500 server error codes are so generic, they are fairly difficult to troubleshoot. Additionally, since it’s a server error rather than a client error, there is likely nothing you can do to solve it.

If you receive a 500 error code, contact the website. Also, it’s always worth a shot to check the URL, refresh the page, and clear your cache.

503 error

HTTP error code 503 means the service is unavailable. Usually, service unavailable error codes mean the site is down for maintenance or overloaded. Typically, this is a temporary state. The best thing to do when you encounter a 503 error is to try again later.

What causes HTTP 400 error?

The HTTP Bad Request error can occur as a result of any of the following issues.

  • A URL string syntax error. Double-check that all the symbols and characters in the URL are correct; a mistyped URL often causes an error.
  • A server error. Sometimes errors occur on the server side, which the user can't control. Try refreshing the browser or choosing a different browser to solve this issue.
  • An oversized file. Each server can only handle data up to a certain size. If your files surpass the file size limit, it can result in an HTTP error.
  • A corrupted cache. If your DNS cache or browser cache contains outdated or corrupted data, it causes an error.

How to fix a 400 Bad Request error

If you're experiencing the HTTP error 400 Bad Request, there are several potential ways to resolve it. Consider trying the following methods if you receive the request error 400 or are having trouble with the way your web server is processing requests.

Clear your browser cache to fix 400 errors

If your browser contains any corrupted files in its local storage, it could return a 400 Bad Request error rather than the requested resources. All files - including HTML, audio, CSS, and data files - need to be in working order. Clear your browser cache to make sure that the files update and function correctly; this can help resolve a 400 error code.

Clear your browser cookies to fix 400 errors

Almost all webpages use cookies to both enhance user experience and gather demographic or performance data. While these small files are typically unproblematic, they can sometimes expire or become infected. If this is the case, you might not be able to reach the resource you requested, triggering a 400 Bad Request error.

You can resolve this issue by clearing your cookies in your browser or on your device. It's a simple process that only takes a few moments, but it can help fix the 400 error code and improve your device's performance overall.

Check the server limits to fix 400 errors

400 Bad Request errors can occur when you upload a file that's too big, surpassing the server file size limit. Visual files, such as image files and video files, most often trigger this issue, as those files tend to be larger in size. If you receive a 400 error, check your server limits and the size of your file. Try uploading a smaller file if this seems to be a problem.

Clear the DNS cache to fix 400 errors

Outdated DNS cache data can also cause a 400 error. Try clearing your DNS cache to reset the data and allow sites to re-cache with any new updates or patches.

Keep in mind that clearing the DNS cache may slow down your webpage loading times temporarily, as the sites are no longer in the cache. However, this only temporarily affects your browsing experience. Clear the cache to see if it resolves the error.