Facebook custom audiences can match either an email address or Facebook ID.
By default Kahuna uses Email address to match users for targeting in Facebook.
Customers will only successfully match when there email address is linked to their Facebook account. Many customers use different email accounts than they link to in their Facebook profile often resulting in a lower match rate.
NOTE: Kahuna's Facebook messaging channel is still in Beta. Please reach out to your sales manager if you are interested in exploring this feature.
If you are interested in using Facebook ID to create custom Facebook audiences instead of email address, please let your Customer Success Manager know or open a support ticket.