# contactsd Canonical page: https://vitalsmac.com/glossary/contactsd Activity Monitor glossary, Processes you will see. What is contactsd on Mac? Also: Contacts sync **Short answer:** contactsd is the macOS process that manages your contacts. It keeps the Contacts database on your Mac, answers every app that looks up a name, number or address, and works with the accounts in Internet Accounts to keep contacts in sync with iCloud, Google, Exchange and other servers. Contacts is not the only app that reads your address book. Mail uses it to put names on senders, Messages and FaceTime to show who is calling, Calendar to fill in invitees, and Spotlight to find people. Each of those asks contactsd, so it runs whether or not the Contacts app is open. Most of the time it is idle and uses almost nothing. It gets busy when there is real work: the first sync after you add an account, a large import, a macOS update that migrates the database, or an account that keeps failing and trying again. The last one is the usual reason it stays near the top of the CPU list for hours. ## Why contactsd is using so much CPU A short spike after you add an account, import a vCard file or update macOS is normal and ends by itself. contactsd is reading, merging and indexing every card, and a large address book takes a while. A spike that never ends usually means one account is stuck in a loop. contactsd asks the server for changes, gets a reply it cannot process, and asks again. Google and Exchange accounts cause this more often than iCloud, typically after a password change, a revoked sign-in, or a group or card the server rejects. Thousands of duplicate cards, often from the same account added twice, keep it busy in the same way. ## How to calm it down Start by finding the account. Open System Settings → Internet Accounts and look for one that asks you to sign in again, then open Contacts and check the accounts in its sidebar for a warning. If one account is the problem, turn Contacts off for it, wait a minute, and turn it back on. contactsd then drops that account's local copy and downloads it again. If you cannot tell which account it is, turn Contacts off for every account except iCloud, see whether contactsd settles, and add the others back one at a time. Quitting contactsd in Activity Monitor only helps for a moment: macOS starts it again straight away, and the same account soon sets it off again. ## How to tell whether contactsd is stuck A sync that is working gets quieter. A sync that is looping looks the same every few minutes. Activity Monitor and Terminal can show you which one you have. 1. Open Activity Monitor, click the CPU tab and type `contacts` in the search field. You will see contactsd, and often AddressBookSourceSync, the helper that talks to each account's server. 2. Watch % CPU for a few minutes. A figure that falls toward zero is a sync finishing. One that stays up, or rises and falls on a steady rhythm, is a loop. 3. Click the Network tab. A loop usually shows AddressBookSourceSync sending and receiving small amounts again and again, rather than one large download. 4. For the detail, open Terminal and run `log stream --predicate 'process == "contactsd"'`. Repeated errors that name the same account or server point at the account to fix. Press Control-C to stop. ## Normal contactsd use vs a problem Normal: contactsd sits near zero, wakes for a moment when Mail or Messages looks up a name, and works for a few minutes after you add an account or import cards. After a macOS update it may be busy for longer while it moves the database to a new format. Worth looking into: it stays busy for hours, the fans come on while you are doing nothing, or Contacts shows the same people two or three times. These are the usual causes: - An account that needs you to sign in again, after a password change or a revoked app password. - The same Google or Exchange account added twice, once in Internet Accounts and once through an app. - Thousands of duplicate cards from an old import. In Contacts, choose Card → Look for Duplicates to merge them. - A work account whose server limits how often you can sync, so every attempt is refused and retried. ## Where contactsd keeps your contacts The database lives in your user Library, in `~/Library/Application Support/AddressBook`, with a folder per account under Sources. Do not delete or edit it by hand to fix a sync problem: turning Contacts off and on for the account in Internet Accounts rebuilds that account's copy safely, and contacts that live only on your Mac are not touched. Before any bigger change, export a backup from Contacts with File → Export → Contacts Archive. It saves every card from every account in one file you can import later. ## Questions people ask ### What is contactsd on Mac? The macOS process that manages your contacts: it keeps the Contacts database, answers apps that look up people, and syncs contacts with iCloud, Google, Exchange and other accounts. ### Why is contactsd using high CPU? Briefly, because it is syncing or indexing after an account was added, an import, or a macOS update. For hours, because an account is failing and retrying, or because the address book is full of duplicates. ### Is contactsd a virus? No. It is part of macOS and is started by launchd under your own user account. You cannot remove it, and there is no reason to. ### What is AddressBookSourceSync? The helper contactsd uses to sync each contacts account with its server. If it is busy along with contactsd, one of your accounts is syncing, and a loop between the two usually points at a single account. ### Will turning Contacts off for an account delete my contacts? It removes that account's copy from your Mac, not from the server. Turn it back on and the contacts download again. Contacts stored only On My Mac are not affected. ## In Vitals Vitals lists contactsd with macOS's own processes, with its CPU, disk and network, so a sync that keeps restarting is easy to spot. ## Related - [cloudd](https://vitalsmac.com/glossary/cloudd) - [launchd](https://vitalsmac.com/glossary/launchd) - [% CPU](https://vitalsmac.com/glossary/cpu-percent) - [mds_stores and mdworker](https://vitalsmac.com/glossary/spotlight-indexing) Looking for something better than Activity Monitor? See [the best Activity Monitor alternatives for Mac](https://vitalsmac.com/best-activity-monitor-alternatives), or [every term in the glossary](https://vitalsmac.com/glossary).