The Auto Login perk allows you to automatically log the user in after they have registered (via a Gravity Form) to your site. Additionally, this perk maintains the existing form confirmation allowing you to display a text confirmation, redirect to a WordPress page, or redirect to a URL with no additional effort.
This perk requires the User Registration Add-On for Gravity Forms. Assuming this add-on is installed and activated, go ahead and navigate to the User Registration page.
On the User Registration page, create a new registration feed as you normally would or edit an existing feed. Scroll to the bottom of your feed and look for the “Auto Login” option within the “Additional Options” group. Check the corresponding checkbox to enable the Auto Login functionality for this feed. With this option enabled, any user that is registered from this feed, will automatically be logged in when the form is submitted.