Converting A Claims-Based Web Application to Classic (Windows) Authentication

To test out the migration of a site from SharePoint 2010 to 2013, I needed to convert a test environment web application to claims authentication to prepare for the move. However, to prove out my methodology and make sure I had the process down, I converted the web app back to classic authentication in order to repeat my steps. I’ve found a number of sites that explain how to do this, but have yet to find it all consolidated into one post. So here’s what I’ve found.

1. First of all, using PowerShell, logged in as the farm account (with admin access on the server and the farm of course) on a server in the farm, run the following commands:

   $setcba = Get-SPWebApplication "http://testapp.contoso.com/"
   $setcba.UseClaimsAuthentication = 0;
   $setcba.Update()

2. In the web.config of the web application, change the authentication section to reflect the following:
   • From:<authentication mode=”Forms” />
     <forms loginUrl=”/_login/default.aspx” />
     <authentication>
   • To:<authentication mode=”Windows” />
3. In IIS Manager, open the configuration page for the site of the web app and change the authentication config for anonymous to disabled.
4. Republish any workflows or SSRS reports that may be necessary to the functionality of the site.

Now if you can’t access the site after performing these steps, that means you need to convert or migrate users back to the DOMAIN\username format from the claims-based i:0#.w|DOMAIN\username format. Not an easy task, but doable. If you alone need access to the site, as an admin, just go into CA and add the farm account back with access to the web app. The quick way around this if other users need into the site is to just take a copy of your production site (presuming it is still using classic auth) and backup/restore it to this newly converted web app.