The 400 Bad Request error is an HTTP status code, which means that the request you sent to the website server was somehow incorrect or corrupted, and the server could not understand it.
400 Bad Request errors appear differently on different websites, so instead of just “400” or another simple variant, you can see something from the short list below:
Bad Request. Your browser sent a request that this server could not understand.
Bad Request - Invalid URL
Bad Request: Error 400
HTTP Error 400. The request hostname is invalid.
400 - Bad request. The request could not be understood by the server due to malformed syntax. The client should not repeat the request without modifications.
The 400 Bad Request error displays the same as web pages in the internet browser window. 400 Bad Request errors could be seen in any operating system and in any browser, like all errors of this type.
How to Fix the 400 Bad Request Error
Check for URL errors. The most common reason for a 400 Bad Request error is that the URL has been typed incorrectly or the link clicked on points to a malformed URL with a particular type of error, such as a syntax problem.
If you get a 400 Bad Request error, this is most likely the problem. In particular, check for additional characters, typically unauthorized, in the URL as a percentage character. Although something like a percentage character has perfectly valid uses, you won’t often find one in a standard URL.
Clear the cooies of your browser, especially if you have a Google service error with a bad request. Many sites report a 400 error when reading a cookie is corrupted or too old.
Clear your DNS cache, which should fix the error of 400 Bad Request if it is caused by outdated DNS records stored by your computer. Do this by running ipconfig / flushdns from a Command Prompt window in Windows.
This is not the same as clearing your browser’s cache.
Clean the cache of your browser. The root of the problem displaying the 400 error could be a cached but corrupt copy of the web page you’re trying to access. Clearing your cache is unlikely to fix most 400 bad request problems, but it’s fast, easy and worth trying.
Although this is not a common fix, instead try to fix the problem as a 504 Gateway Timeout problem, even if the problem is reported as a 400 Bad Request.
Two servers may take too long to communicate in some relatively rare situations (a gateway timeout problem), but they will report the problem to you incorrectly or at least unhelpfully as a 400 Bad Request.
If you upload a file to the website when you see the error, the 400 Bad Request error is likely because the file is too large, so the server will reject it.
If the 400 error occurs on almost every website you visit, your computer or internet connection is most likely the problem. Run an internet speed test and check it with your ISP to ensure that everything is properly configured.
Contact the website hosting the page directly. The 400 Bad Request error may not actually be wrong at your end, but rather something they need to fix, in which case it would be very helpful to let them know.
For ways to contact a number of popular sites, see our Website Contact Information list. Most sites have contacts with social networks and sometimes even phone numbers and email addresses.
If a whole site has a 400 Bad Request error, it is often helpful to search Twitter for #websitedown, such as #facebookdown or #gmaildown. It will certainly not help fix the problem, but at least you’ll know you’re not alone!
If nothing has worked above, and you’re sure your computer doesn’t have a problem, you’re left to check back later. Since the problem is not yours, you should regularly visit the page or site until it is backed up.
More Ways You Might See a 400 Error
In Internet Explorer, the message of a 400 Bad Request error is not found on the web page. The IE title bar says HTTP 400 Bad Request or something similar.
Windows Update may also report errors in HTTP 400, but the error code 0x80244016 or WU E PT HTTP STATUS BAD REQUEST will be displayed.
A 400 error reported for a link in a Microsoft Office application is often reported as an error returned by the remote server: (400) Bad Request. Message in a small window pop-up.
Web servers running Microsoft IIS often provide more specific information about the cause of a 400 Bad Request error by suffixing a number after 400, as in HTTP Error 400.1 -Bad Request, which means invalid header of destination.
Here’s a complete list:
|Microsoft IIS 400 Error Codes|
|400.1||Invalid Destination Header|
|400.2||Invalid Depth Header|
|400.3||Invalid If Header|
|400.4||Invalid Overwrite Header|
|400.5||Invalid Translate Header|
|400.6||Invalid Request Body|
|400.7||Invalid Content Length|
|400.9||Invalid Lock Token|
More information about these IIS-specific codes can be found on page IIS 7.0, IIS 7.5 and IIS 8.0 of Microsoft’s HTTP status code.
Errors Like 400 Bad Request
A number of other browser errors are also client errors and are therefore at least somewhat related to the error of the 400 Bad Request. Some include 401 unauthorized, 403 prohibited, 404 not found and 408 timeout for requests.