SharePoint: “HTTP 400 Bad Request (Request header too long)” Error Fix

I recently came across this issue on our internal SharePoint deployment and tried a few things to fix it without success. Initially, I thought it may be to do with the sheer quantity of Active Directory groups I was a member of, however after reducing the number of groups I was a part of there didn’t appear to be any change in the issue.

After looking around and attempting a few fixes I finally came across why the issue occurs and how to fix it. I’ll cover all of this in this article.

The Issue


The issue occurs when the browser tries to access SharePoint and creates an HTTP request which includes anĀ authorization token which is either too large for IIS to handle or is corrupt. From some research online I’ve found that this can be caused by the number of Active Directory groups a user is a part of which may also be worth checking.

The Solution

The quickest way to resolve the issue is to simply clear all cookies from the browser you use, this can be done in most browsers by pressing CTRL + Shift + Delete on your keyboard when the browser is selected and then clearing the following depending on browser –

  • Chrome – Cookies and other site data
  • Internet Explorer – Cookies and website data
  • Firefox – Cookies

However it is also possible to simply delete all of the cookies for the affected site, the links below will help you to do this –


Hope this helps, any issues get in touch below


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