YOU ARE BEING WATCHED.

• Author: Lazarowitz, Elizabeth
• Position: MEDIA LITERACY

Marketers are tracking what you do online so they can target you with ads matching your interests. What does that mean for your privacy?

Kelsey Marques, 17, knew it couldn't be a coincidence when ads for a Chevy Malibu showed up on websites she viewed just a day after she had searched online for that exact car.

"It's a little creepy," says the high school senior from Clark, New Jersey.

Even creepier, she says, is how her Instagram account seems to know so much about her--suggesting things like cheerleading videos or hair and makeup tutorials--just based on the kinds of posts she "likes" or users she follows, she says.

"It's a little bit weirder just because they're using your personality," she says. "They're developing a profile of you." The reality is that whenever you're on the web, you're being watched. Companies are gathering all the information they can about you: your friends, where you live, the videos you watch, the games you play--and maybe even how you're feeling. Their goal is to sell your digital dossier to marketers, who use it to try to show you digital ads that match your tastes.

For privacy advocates, it's all too close for comfort. Critics charge that much of this corporate data digging is done without users' direct consent, and that it's hard--if not impossible--to opt out of the tracking (see "Stop Following Mel," facing page). And it can even lead to discrimination.

"Commercial surveillance has been baked into the foundation of the internet,"says Jeff Chester of the Center for Digital Democracy, a digital privacy watchdog. "When you sign onto Facebook, you're signing your digital life away."

Data for Sale

Data trackers--which include web giants like Google and Facebook--say the information they collect is made anonymous and dumped into broad categories such as "male sports fan ages 18-24 in Montana." Marketers argue that seeing ads for things you're likely to buy is less annoying than seeing random ads, and that the ads support content we've come to view as free, like Facebook, Gmail, and many websites.

"Today, advertisers can understand their audience better and more quickly because of how often people go online and all the things they do online," says Richard Joyce, a digital advertising analyst at Forrester Research. "The concept of it is, 'We want to make something better for the customer.'"

A lot of money is at stake in the race to get to know you. Spending on digital advertising overtook spending on TV ads for the first time ever in 2016 and was poised to hit $83 billion in the U.S. in 2017, according to eMarketer.

Companies dig up data largely through cookies, little lines of code that many websites implant into a computer's hard drive the first time a user visits. Basic cookies can save login information, user preferences, and items in a consumer's shopping cart. But so-called third-party cookies can track a user within a whole group of websites. That's why after you've been reading about sports on one site, you might see ads for sneakers on other seemingly unrelated sites.

And increasingly, companies are syncing up what you do online with what you do in the real world. Last May, Google said it was partnering with credit card companies so it could tell advertisers...