How to find and merge duplicate contacts

Martin writes: Since converting from Microsoft to Apple, all my contacts have been duplicated—sometimes up to five times!
Some information is coming from Outlook Contacts but I can’t find the source and iCloud seems to be procreating without any help.
Please help me to eradicate these multiple contacts and regain my sanity.
Hi Martin! Sounds like there was a little confusion while your address book was making its way from your Windows PC to your Mac—and yes, it’s pretty annoying to get five results for a contact search when you were looking for just one.
Luckily, there’s a fairly easy way to seek out and merge duplicate entries in the Mac’s Contacts app.
Here’s how…

• First, make sure to back up your address book before you start merging or deleting any contacts. Open the Contacts app, click File, Export, then Contacts Archive. Pick a place on your Mac’s hard drive that’s easy to remember (like the Documents directory), then click the Save button.
• Next, click the Card menu at the top of the screen, then select “Look for Duplicates.”
• After scouring your address book for a few seconds, the Contacts app will report back with its results. For instance, when I recently checked for duplicate contacts, I got a message that read: “17 duplicate cards and 10 duplicated entries were found.”
• Now, time for the moment of truth. Click the Merge button to let your Mac merge any duplicate contacts it found. Unfortunately, you can’t review the changes before they’re made—and that’s why it’s so important to make a backup before the merge.
• Once the “deduping” process is completed, give your contacts a look. See anything you don’t like? If so, you can restore the backup you made by clicking File, Import, and then selecting the Contacts archive you saved earlier.
• If, on the other hand, everything looks good, then you’re all set—and remember, if you’re an iCloud user (and it sounds like you are, Martin), all your merged contacts should sync automatically with any iCloud-connected iPhones and iPads.

Source: heresthethingblog.com
How to find and merge duplicate contacts