SharePoint 2010 Error: HTTP Error 400. The size of the request headers is too long

Recently I started seeing this error on our internal TFS SharePoint sites.  These sites use the Excel Dashboards and if I opened more than a few sites at a time, I would start getting the following popup error:

Unexpected callback response!
Error: 400 Bad Request

Bad Request - Request Too Long
HTTP Error 400. The size of the request headers is too long.

It didn’t seem to matter which browser I used or whether I ran in Private Mode (to get a clean session each time) – the result was always the same error.

The fix:

Save this as a .reg file and run it.

Windows Registry Editor Version 5.00


After setting the settings, you will need to restart your server so that HTTP.sys can pickup the new parameters.

Comments (5)
  1. Kathryn Janeway says:

    I have a Sharepoint 2010 site where just one user is receiving the "HTTP Error 400. The size of the request headers is too long." error.  It happens in all browsers and happens across different machines when the user is logged in with his credentials.  I've cleared the users cache, opened the browser in safe mode, and he is still not able to get to the site. Any ideas?

    Additional info: User is able to hit other servers/sites without a problem.

    Any suggestions?

  2. Grant says:

    @Kathryn – see the KB…/en-us

  3. Efosa says:

    God bless you man! :) A lot was riding on me finding this page and implementing this fix!

  4. Kyle says:

    I am having some issues upon installation of SharePoint 2010. After immediatly installing SP 2010 configuration wizard, It takes me to the SP Central Admin Site.  However, I get an HTTP 400 Error.  This occured after I uninstalled and reinstalled SP 2010.  Does anyone have any idea of what might be causing this?  I am running it on SQL server 2008 r2.  I have tried to uninstall and reinstall several times.  I even totally uninstalled SQL Server 2008 and all it's components, VS, and SP and reinstalled to no avail.

  5. jenitta says:

    Thank you so much for such informative post.I am very happy to knew about it .keep up the interesting post……/sharepoint-2010-root-of-certificate.html

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