BusyContacts is a client app that syncs with a server. Typically, the built-in Contacts app on macOS and iOS is configured to sync with either iCloud, Google or Exchange, all of which are compatible with BusyContacts.

This means any data you enter into the built-in Contacts app on macOS and iOS will sync to BusyContacts, and vice versa, through the server. As long as you have all clients configured to sync with the same servers, all of your contact data will remain in sync.

BusyContacts syncs with all leading address book servers, including iCloud, Google, Exchange, Fastmail, macOS Server, Kerio, Zimbra, and other CardDAV servers.

You can connect to a server by selecting BusyContacts > Settings > Accounts, clicking the + button, choosing a server type, and entering your username and password.

For more info see:

• Using BusyContacts with iCloud
• Using BusyContacts with Google
• Using BusyContacts with Exchange
• Using BusyContacts with Fruux
• Using BusyContacts with CardDAV
• Using BusyContacts on a LAN