I have an site collection in a web application for which I need to enable forms based authentication (rather than using the standard Windows/AD authentication).

I followed the rather good instructions at http://donalconlon.wordpress.com/2010/02/23/configuring-forms-base-authentication-for-sharepoint-2010-using-iis7/ and confirmed that the web.config files are properly setup after having gone through this procedure.

The problem I have is that I do not get a authentication login web page when going to any of the sites in the collection - I should get a drop-down asking if I want to use forms-based or windows-based authentication. Instead I get a straight web-browser pop-up username/password dialogue. Furthermore, I cannot login using this dialogue.

Creating a new web application and new site collection within does give the expected web page with the choice of authentication method, and I can log in there using the forms-based user.

So what's the magic for enabling this on an existing web application/site collection?

1 Answer 1


You have to create an "extended webapplication" for using different authentication mechanisms for a single web application that is already created on SharePoint. You can do this through the central administration as mentioned here .

The instructions you followed are pretty much same for enabling FBA for the extended web application.

Please follow this link from microsoft that precisely explains why there is a need for having an extended web application and how we enable FBA on the same. This is fairly necessary to understand if you are planning for some extranet deployments.


  • That's excellent - many thanks. The downside with this is that I will need to extend to an additional IIS web application. I cannot simply extend the existing web app because that throws an error that it is already used by SharePoint. This is unfortunate because the final design calls for one web app only, all being authenticated via forms-based authentication (the whole web app will be extranet in effect).
    – nroam
    Jul 3, 2012 at 14:16
  • Final summary: In the end I backed-up the existing site collection to a file using the PowerShell. Then I dropped the web application and then built it up from scratch but using FBA instead as described in the various links above. I then imported the site collection again and all is well.
    – nroam
    Jul 4, 2012 at 11:57
  • Its a decent workaround. Just ensure that you use this method with some added precautions if your site contains workflows and event receivers. Workflow states are lost when restored to another web application if the features referred by the workflows are not deployed before the restore.
    – ArkoD
    Jul 4, 2012 at 12:40

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