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When you visit a stranger's Facebook profile, you may notice that the "Add Friend" button is missing. This is because that person has set their security settings so that they only receive friend requests from people who share at least one mutual friend. You'll need to be friends with at least one person on this person's friends list before you can send a friend request. Many people have their friends list public, allowing you to send friend requests to people on their friends list. You'll see a list of all the person's friends (if their list is public). If the "Friends" tab does not display any friends, you'll have to hope that you eventually make some mutual friends with this person. Look for posts that they comment on and send friend requests to the original poster. Once at least one accepts, you'll be able to send a friend request to the original person. When you view a friend's list of friends, you'll see all of your mutual friends at the top. After you scroll through your mutual friends, you'll see people that have mutual friends with you, sorted by the number of mutual friends you both have. You'll be able to send friend requests to any of these people by tapping or clicking "Add Friend."
Add mutual friends if you can't add someone as a friend. Tap or click the "Friends" tab on their profile page. Find people to add. Send friend requests. Add friends from your own friends' lists.