How to delete multiple contacts at once from your iPhoneWho are all of these people and why are they in my Contacts list and how do I get rid of them all at once?
Updated March 2017: Updated steps to reflect changes to version 3.6.2 of Groups.
By default, your iPhone will only let you delete contacts one at a time, which isn't a very pleasant process for anyone who has lots to delete. For those that don't want to go the nuclear option of deleting all of them via iCloud, these is a way to delete multiple contacts at once, you'll just need the help of an App Store app to do it.
Get Groups in the App Store
How to delete multiple contacts from your iPhone all at once
Download the Groups app on your iPhone.
Launch the Groups app on your iPhone.
Grant Groups access to your contacts when prompted.
Select All Contacts from the Groups list.
Go through your contacts and mark the ones you'd like to delete by tapping on the circle outline to the left of their name.
Tap Choose Action at the top.
Tap on Delete contacts... in the popup me...
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How to delete multiple contacts at once from your iPhone
