Change SharePoint 2010 Authentication from Windows to Forms

While creating a web application, by mistake selected “Windows” authentication, and felt we need “Forms” authentication (Claims Based Authentication) because of a business requirement.

Went to Central Administration >> Application Management >> Manage Web Applications >> Selected the desired web application >> Authentication Providers.

Oops, “Forms” option is disabled! Couldn’t find any way to enable “Forms” Authentication from user interface. Solution? PowerShell!

Add-PSSnapin Microsoft.SharePoint.PowerShell -ErrorAction SilentlyContinue 

$WebApp=get-spwebapplication "http://sharepoint.crescent.com"
$WebApp.useclaimsauthentication="True"
$WebApp.Update()