Duplicate contacts on iCloud and Apple devices

Actually, I managed to solve this problem in a few minutes by visiting https://www.icloud.com/settings/, scrolling down to "Advanced settings", clicking "Restore contacts" and then roll back to an older backup of my contact list (before the Big Sur update). Now all my duplicates are gone ☺️

I've got the same problem of duplicated entries (exact dups) on my iPhones and my MacBook right after I upgrade my MacBook to Big Sur. The duplication happens on the database in iCloud, not just on the phone.

Search this thread and apply the workaround is to login to your iCloud, scroll down to Advance Setting and choose restore the Contact list from the last backup, which in my case 2 days ago.

The restoration popped up some error message when I did on the Big Sur. I tried it again and this time it is successful. Losing the changes for the last 2 days but usually we do not have much changes in the Contact. So, this is the fast and most effective way.

Lesson learn: if you have another MacBook or multiple of them, do not perform another upgrade until next month when Apple gives out another patch or 2nd release to fix the issue or you will have another duplication or triples

I believe I've finally resolved my contacts issue. I wanted to outline my entire experience here in case it helps anyone else. I estimate about 5 hours were put into figuring this out over some days. 

CONCISE VERSION

- Don't upgrade to Big Sur yet if you have synced Google contacts.

- If it's too late, and you have duplicate contact issues, back them up as vCards first even if there are duplicates - I had issues importing the previous 'Contacts Archive ...' method. Select all contact cards, and then 'File -> Export -> Export vCard ...'

- Disable contact sync in "Internet Accounts" on Mac on all but one computer if you have multiples.

- Resolve duplicates on that machine again and again. 'Card->Look for Duplicates ...'

- If this doesn't work, delete them all (if they are backed up of course). Then wait for everything to resync so there are no contacts left on any machines.

- Next, importantly, Google has its own trash (https://contacts.google.com/trash) for contacts that needs to be emptied or it will throw a (silent or vague) error while trying to generate new or sync contact changes. If you're in the browser you'll see this: "Trouble creating contact. [object Object]"

- Empty Google Trash over and over until it's completely empty, wait, then reimport the vCards on one machine, and wait for them to propagate to the others. 

- Resolve duplicates at this point if necessary.

FULL VERSION

- After installing Big Sur on two machines, my Google contacts kept duplicating, at times I was up to 57 contacts for each original contact.

- In Apple Contacts App on Mac, I ran the 'Card->Look for Duplicates ...' clean-up command which seemed to work on that particular machine, but it would often not help on another machine.

- After keeping at this, it seemed to stabilize. But, I realized I could now no longer make new contacts, and syncing wouldn't occur. 

- After trying every combination of adding / deleting contacts on each machine and via browser, I determined that it was now an issue with Google Contacts and no longer Mac - it had spread somehow. I would get this error in the browser: 'Trouble creating contact. [object Object]' - I couldn't find any solutions when Googling this, which is in part why I'm writing this. 

- It turns out that Google Contacts has its own Trash which must be accessed via browser: https://contacts.google.com/trash The trash was filled up with ~50,000 contacts. There must be a limit on contact storage, I realized, and the trash had been filling up with all of the sync errors, and subsequent resolves of duplicates.

- It took many passes of pressing "Empty Trash now" at the top of the screen. I had already deleted all of my contacts for tests. I was then able to create and alter contacts successful via each computer and browser. Once that was confirmed, I reimported my backed up vCards. 

- I see that an update for Big Sur, 11.1 is now available. I'm hoping that will help this issue. 

- Recommendations: see above, or: back up from Apple Contact as vCards *before* upgrading to Big Sur, or better, wait until this issue is resolved. If you're here, I'm assuming it's too late ...

Try - If you see duplicate contacts after setting up iCloud Contacts - Apple Support.

I was able to use google contacts to remove the duplicates. It has a dup find and merge function. Took multiple passes and about an hour. I also turned off the contacts synch between google and my MacBook look under internet accounts and uncheck the “Contacts” box in your google account settings.

Check if you are using Gmail or Hotmail as well as iCloud for contacts. Gmail certainly appears to have duplicated all contacts on that platform following the Big Sur update applied to my iMac. Easy fix - go into Google Mail | Contacts (or presumably Hotmail if you use that) and there you will find simple tools to remove duplicates /merge all in a few simple steps. Takes a short time to update back to the iOS devices, check Gmail on each device to force update and this will do the contacts also in a few seconds.

This happened to me after the bug sur update and my contacts multiplied by 8! I downloaded an app called cleanup duplicate contacts and it worked instantly

Same issue here, but with Google contacts. In some cases there are 30+ duplicates of a single card. I had over 20,000 contacts up from 1,100.

Using the Mac OS Contact app, you can choose Card -> Look for Duplicates ... and then merge the data.

However, the duplicates will soon return, meaning this isn't a one-time error when the OS updates—it's continuous and must happen each time there's a sync.

If you're using Google contacts, don't make the mistake of merging the data via the browser, as it does a poor job that results in many duplicates of the address under a single card.

10th Jan 2021 I updated to Big Sur and this issue is still here. Contacts are all duplicated 4 times, Come on Apple, you've really dropped the ball on this entire operating system. I was forced to update because my Macs were all still on Mojave and they started crashing after you released BigSur and you said I had to update to to fix.

I also have duplicates on my Iphone , MacBook and Icloud after the Big sur update

and in Icloud Contacts - i have a lot of Cards that contain different numver of contacts

Same problem. After installing big sur all the contacts on iphone doubled

Mine actually tripled.

There should be a way to remove them en masse as opposed to one at a time.

Same problem here... All my contacts are duplicated.

This isn't limited to iCloud, unfortunately. I have the same issue with contacts synced with a CalDAV server.