The 400 Bad Request error is an HTTP status code that means that the request you sent to the website server, often something simple like a request to load a web page, was somehow incorrect or corrupted and the server couldn’t understand it.
The 400 Bad Request error is often caused by entering or pasting the wrong URL in the address window but there are some other relatively common causes as well.
400 Bad Request errors appear differently on different websites, so you may see something from the short list below instead of just “400” or another simple variant like that:
400 Bad Request
Bad Request. Your browser sent a request that this server could not understand.
Bad Request - Invalid URL
HTTP Error 400 - Bad Request
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 inside the internet web browser window, just as web pages do. 400 Bad Request errors, like all errors of this type, could be seen in any operating system and in any browser.
In Internet Explorer, “The webpage cannot be found” message indicates a 400 Bad Request error. The IE title bar will say HTTP 400 Bad Request or something very similar to that.
Windows Update can also report HTTP 400 errors but they display as error code 0x80244016 or with the message WU_E_PT_HTTP_STATUS_BAD_REQUEST.
A 400 error that’s reported for a link within a Microsoft Office application will often appear as a The remote server returned an error: (400) Bad Request. message within a small pop-up window.
Note: Web servers running Microsoft IIS often give more specific information about the cause of a 400 Bad Request error by suffixing a number after the 400, as in HTTP Error 400.1 – Bad Request, which means Invalid Destination Header.
Important: This is most likely the problem if you get a 400 Bad Request error. Specifically, check for extra, typically non-allowed, characters in the URL like a percentage character. While there are perfectly valid uses for something like a % character, you won’t often find one in a standard URL.
Important: This is not the same as clearing your browser’s cache.
In some relatively rare situations, two servers may take too long to communicate (a gateway timeout issue) but will incorrectly, or at least unhelpfully, report the problem to you as a 400 Bad Request.
See our Website Contact Information list for ways to contact a number of popular sites. Most sites have social network contacts and sometimes even telephone numbers and email addresses.
Tip: If an entire site is down with a 400 Bad Request error, searching Twitter for #websitedown is often helpful, like #facebookdown or #gmaildown. It certainly won’t contribute anything to fixing the issue, but at least you’ll know you’re not alone!
Since the problem isn’t yours to fix, revisit the page or site regularly until it’s back up.
If you’ve followed the advice above but you’re still getting a 400 Bad Request error when trying to open a certain web page or site, see Get More Help for information about contacting me on social networks or via email, posting on tech support forums, and more.
Be sure to let me know that the error is an HTTP 400 error and what steps, if any, you’ve already taken to fix the problem.