It started because Kelsey McKinney wanted to know where her sister was every single moment of the day.

“I like to call her and she likes to call me and it was only practical to share our locations so that we would know whether or not now was a good time to call without asking,” said Ms. McKinney, a 31-year-old journalist and the host of the podcast Normal Gossip. The sisters began sharing their locations using their iPhones’ Find My Friends feature, which allows users to visualize all of their location-sharing friends on a global map.

“Pretty quickly, I came to love looking at her little dot,” Ms. McKinney said. “It was affectionate to me, and I started asking my friends to share their locations with me, or just sharing my location with them and hoping they would reciprocate.”

Location sharing has long been the domain of parents with wayward teens or obsessive partners, but more and more, apps like Find My Friends are being used by young people who want to know where their friends are and what they’re up to, without actually having to ask them.

Most smartphones offer location sharing capabilities, but since more than half of Americans use iPhones, Find My Friends is by far the most popular.

Apple’s Find My function wasn’t conceived as a way to lovingly stalk your pals, but that’s what it has slowly become. When it debuted, in 2009, as Find My iPhone, the app allowed users to employ GPS data to track their lost iPhones; Find My Friends came two years later, marketed to anxious parents who wanted to keep tabs on their children.

In 2019, the company integrated its location-tracking capabilities into a single app, called Find My, which lets users see the location of their friends and Apple devices. Since then, Find My Friends has become a digital calling card of sorts, a way to express tenderness and intimacy between close friends and draw a distinction between them and the rest of their online acquaintances.

Courtney Trop, a Los Angeles style blogger and the founder of Stevie, a CBD brand, said she used Find My Friends with about 15 people, including her best friend, Perry. “We use it to stalk each other to see if we went on shopping trips without each other,” Ms. Trop said. If she is revealed via Find My to be shopping unaccompanied, her friend lets her have it in a cascade of “crazy messages”: “You went without me! Oh my God, I can’t believe you’re at Replica right now!”

Several people said they used the app to track friends when they were going on Tinder dates, or to make sure they got home safely after a night of partying. It came in handy for Kevin LeBlanc, 25, a fashion associate in New York, when his friend passed out on the street one evening, and he used the app to locate her. The friend’s mother told Mr. LeBlanc that her daughter was in an ambulance and asked him to follow it. “I had her location on,” he recalled, “so I knew exactly where she was.”

When the coronavirus pandemic forced Americans to turn to the internet for entertainment, home delivery and more, awareness of the way companies and governments use the personal data we publish online also increased.

Yet despite this growing discomfort, there’s also a sense of powerlessness, a general resignation to the idea that the internet is an inescapable part of modern life, and that forking over your data is just part of the bargain. A 2019 Pew Research Center survey found that “some 81 percent of the public say that the potential risks they face because of data collection by companies outweigh the benefits, and 66 percent say the same about government data collection.” Pew also found that most Americans “feel they have little or no control over how these entities use their personal information.” If tech giants and governments have access to your personal data, some may think, why shouldn’t your friends and family?

Apple’s Find My App uses end-to-end encryption, which means the company can’t technically see the locations of its users, but that doesn’t mean everyone is comfortable with sharing their locations with the company or with their friends. Ms. McKinney said that she had a few friends who don’t feel comfortable sharing their locations, but that she wasn’t a stickler for reciprocity. “Some of my buddies are private and don’t want me to see their location, but that’s fine: They must see my location anyway,” she said.

It’s true that there is perhaps nothing more intimate than having live location sharing on — the level of trust you have to have in someone to willingly disclose just how much time you spend sitting in your apartment watching TV! But location sharing can also provide a feeling of closeness even when you’re far away.

Ms. McKinney acknowledges that part of the appeal of the app comes from the fact that she’s “extremely nosy.” “But I also think it provides me a feeling of safety to know that my friends are OK,” she said. “It is comforting even to look at my list and be like, ‘These are all my pals, and they exist in the world even if they are not here with me.’”

A trend on TikTok in which people share screenshots of their Find My Friends maps seems to have arisen from the same sentiment: “Me checking find my friends to make sure all my sims are where they’re supposed to be,” one user wrote.

For Matt Brown, 31, an executive coordinator at a hedge fund in New York, Find My Friends is less a casual pastime than a lifestyle. “I’m always preaching that Find My Friends is my favorite app,” he said.

Mr. Brown currently tracks the location of 47 of his friends across the world. “As somebody who lives in New York, spontaneity is really hard,” he said. “It’s hard to just be like: ‘Hey what are you doing right now? Do you want to grab dinner?’”

He said he loved Find My Friends because no matter where he is in the city, someone he knows is probably close by. “I’ll be like: ‘Hey, what are you doing right now? I’m at this bar — do you want to come meet me?’”

Ms. McKinney also called Find My Friends her favorite app. “My favorite thing to do is to award one of my friends Dot of the Week for being the most interesting dot to watch that week,” she said. One of her friends recently won Dot of the Week two weeks in a row for her trip to Europe. “I was following her little dot in Rome, and I was so happy every day to see that she was somewhere else having fun!”

Of course, Find My Friends is only as accurate as the GPS data it has access to; almost everybody who uses it religiously has a story about the panic that set in when someone’s dot appeared in a place it shouldn’t. Mariel Tyler, a photographer in New York, said that once when she went to check on her sister’s location during a Tinder date, the app said that she was in “the Hudson River.” Ms. McKinney was recently staying at a hotel next to a hospital, which sent one of her friends into a spiral when she checked the app and thought Ms. McKinney had been hospitalized.

To a generation who grew up alongside the internet, location sharing may feel less like a privacy threat and more like an expression of affection and trust. Using Find My Friends requires the ability to put jealousy or FOMO aside and feel nothing but joy for the friend whose little dot is ricocheting around MetLife Stadium, even if she got Taylor Swift tickets and you didn’t. Feeling happy when your friends are thriving, even at times when you might not be, is the purest expression of friendship. As one Twitter user put it: “I love find my friends.. Like aww that’s where my friends are :)”