Google includes a unique identifier on Android devices, called Advertising ID, that allows marketers to see what a user is doing across all apps, allowing companies to build a comprehensive picture of that person's interests and activities. Wednesday's move will limit apps' ability to capture that information.
The company offered few details on what the more private advertising will look like.
Google's move follows Apple's decision last year to limit user tracking on iPhones. Apps on iOS, from diet and fitness apps to mobile games, must now ask for permission every time they track someone. About three-quarters of iOS users choose not to be tracked, according to Flurry Analytics. That's caused waves in the multibillion targeted advertising market.
Apple's privacy push has already slammed Meta, the parent of Facebook and Instagram, with losses. The company said this month that the privacy changes would cost it $10 billion this year — an admission that contributed to a record stock drop, wiping $300 billion off its market value. Meta's stock fell further on Wednesday morning, dropping 3.4% in early trading after Google's announcement.
Some 85% of global cell phone customers use Android, according to IDC.
"Advertisers are reliant on the current tracking mechanisms, and Advertising ID, just like they are on cookies, because it allows them to have a broader picture of their consumers," said Lauren Wetzel, chief operating officer at InfoSum, which describes itself as a privacy-focused data company.
The coming changes mean that many advertisers will have less information on potential customers, Wetzel said. "If you're a publisher, and you're basically trying to showcase to brands and say the advertising that you sell will reach your audience, you also have a lower understanding of your audience," she said, adding that the changes will affect mobile-first companies hardest.
Meta has settled multiple lawsuits alleging it tracked users after they logged off and scanned users' faces without their consent. Last month, four attorneys general sued Google, accusing the company of tracking users' locations and lying about it.
Google criticized Apple's privacy changes in its Wednesday blog post, calling it a "blunt" approach that was ineffective and that could "lead to worse outcomes for user privacy and developer businesses." The company implied that simply turning off tracking would threaten users' ability to get free mobile content.
"Mobile apps are a core part of our everyday lives. Currently over 90% of the apps on Google Play are free, providing access to valuable content and services to billions of users. Digital advertising plays a key role in making this possible," the company said in its post.
Google also said it will seek feedback on its changes from developers, regulators and privacy advocates.
The two-year timeline on those changes shows that the company is trying to strike a balance between privacy protection for users and the interests of advertisers, Wenzel said.
She added, "I don't see the current wave of privacy, and consumers' focus on that, going away."