The Ad Builder Player features an API which allows a custom snippet of code to be added to a project. This creates the opportunity for unique functionality within the ad, which would not be possible using just the native options available in the Ad Builder interface.
Learn more by taking a look at the Ad Builder Player API, this can be found by opening the custom code panel within Ad Builder and selecting the documentation link in the lower left hand corner of the panel.
Opening the Custom Code panel
To open the Custom Code panel, click the 'Menu' icon and select 'Edit Custom Code'. This will open the panel to enter a custom code snippet into the interface.