This plugin allows you to use $_COOKIE, $_SERVER and $_SESSION data in a Gravity Form through the merge tags of a field. I’ve only really tested this using a hidden field.
Instructions
- Copy the plugin files to <code>wp-content/plugins/</code>
 - Activate plugin from Plugins page
 - Add a hidden field to your Gravity Form
 - Go to the Advanced tab in the field settings and hit the down arrow to the right of the Default Value text box
 - Scroll down to Custom and choose either Cookie Data, Server Data or Session Data
 - Change the “key” text with the data you are looking for
 
Got Suggestions or Improvements?
Use the github repository.