Contacts for Mac: Merge contact cards
If you have more than one card for a contact in an account, you can merge the cards. Merging cards combines the cards and keeps all the unique information in a single card.
Look for duplicates: Choose Card > Look for Duplicates.
Merge duplicate cards that are found: Select the cards you want to merge, then choose Card > Merge Selected Cards.
When you use several accounts in Contacts, you may end up with several cards for a contact—for example, one card from LinkedIn and one from Google. You can link the contact’s cards to streamline your list of contacts without merging the cards.