The Contacts app is probably one of the most neglected apps on your Android phone. Your email, SMS , and phone apps use your contacts, so it's important to clean them up regularly. We'll show you how to merge duplicate contacts on Android.
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What is a “duplicate contact?” You can easily end up with two instances of the same person, one with a phone number and one with an email address. The good news is that you don’t have to find these duplicates yourself.
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Merge duplicate contacts with Google Contacts
Google offers its own simple “Contacts” app for all Android devices. If it’s not already on yours, you can download it from the Play Store.
First, open the app and make sure you're using the correct Google account—if you have multiple—by tapping the profile icon in the search bar. You can change here if necessary.

Now you can go to the “Fix & Manage” tab at the bottom of the screen.

Select the “Merge & Fix” tool.

Google will find all the contacts it thinks could be merged. Tap “Merge Duplicates” to review the suggestions.

Look at the suggestions and click “Merge” or “Dismiss” on any of them. If everything looks good, you can merge them all in one go with the “Merge All” button.

You're done! The contacts will now appear as one, with no more duplicates.
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Merge duplicate contacts with Samsung contacts
The default “Contacts” app on Samsung Galaxy devices has a tool for merging duplicate contacts. Let’s open the app to get started.

Tap the menu (three horizontal lines) on the left side of the screen and select “Manage Contacts.”

Select “Merge Contacts.”

There are three sections on this screen. Duplicate contacts are organized by the part that is duplicated: “Number,” “Email,” or “Name.” Select any of the contacts you want to combine or tap “Select All.”.

Tap “Merge” at the bottom of the screen.

That's it! Your contacts will now appear as one. It's very easy to get lost in contacts. Luckily, both Google and Samsung offer easy methods to help you organize things.
Information source: howtogeek.com
