In this blog we are explore how to convert an existing web application configured with Classic Mode Authentication to Claims Based. This can be done using PowerShell.
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Note: Once converted from classic to claims, you will not be able to revert the change.
Screen shot showing web application in Classic Mode:
Now, run the PowerShell command:
$App = get-spwebapplication "http://SvrName:1007"
$app.useclaimsauthentication = "True"
You can see the web application is now converted to Claims Based Authentication: