The lifespan of the tracking cookie is about to expire. With the rapid emergence of mobile devices, the big three — Facebook, Google, and Apple — have turned to new and more potent methods for advertisers to keep track of you across multiple devices.

The impending death of the cookie can be traced to the launch of the iPhone in 2007. Apple initially restricted third-party cookies in iPhones because it believed advertisers would be able to garner too much personal information as they tracked you across websites, according to Medialets chief executive Eric Litman. Third-party cookies still work on Google’s Chrome browser and the Android OS, but they don’t function effectively on a large number of smartphones and tablets produced by other companies. Also, because cookies are not shared between the browser and apps on the same device, they have very limited relevance on mobile devices.

Here’s how each of the big mobile players is trying to replace the cookie with its own brand of tracking.

Facebook

For Menlo Park, California-based Facebook, it all comes down to the billions of metric tons of highly personal metadata the company has amassed from its 1.3 billion users, such as shoe size, hair color, where your grandmother is buried, and where you went to school, for example.

The social network relies on its SSO (Single Sign-On) to follow the movement of users. SSO allows you to use your Facebook credentials on third-party websites and apps. When you do this, Facebook is watching, following, and cataloging your destination points. This data drives, to a degree, what ads turn up on your Facebook news feed. Maybe you’ve noticed.

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Facebook-owned apps, WhatsApp and Instagram, along with the company’s internally developed apps like Messenger and Paper, increase the data flow, though for now, these apps don’t yet feature ads.

But this method only works within Facebook’s ecosystem. The company is looking to expand and recently unveiled a new version of the Atlas ad platform (which Facebook acquired from Microsoft last year) at Advertising Week in New York. The new platform is Facebook’s attempt to serve ads outside its existing ecosystem, on both desktop and mobile.

Google

Like its Facebook friends just down the freeway, Google also relies heavily on its SSO. Logging into any of your Google accounts ties you to the entire Google network, which is massive.

And then of course, Google has its Android mobile operating system, which assigns each user a Google Ad ID. Many of Google’s ad products — AdSense, AdMob, and DoubleClick — pull in your device’s ad identifier. Together with the information it already has from its many web properties, including YouTube, Gmail, Voice, and Search, the company can compile a dossier, as it were, of your digital history. The websites you visit tell Google plenty, and the information comes in handy no matter what device you’re using.

Apple

As for Apple, its tracking techniques are focused primarily on two things: your email address, which ties you to all of Apple’s services running on any iOS or OS X device, and your iTunes account, which gives Apple your credit card data and ties you most closely to its ecosystem.

Your login identity is tied to your Apple “identifier for advertisers,” or IDFA. It’s a unique string of characters assigned to every user buying and using an iOS device. So when ads run on Apple’s advertising network iAd for example, Apple is able to determine who’s receiving the ad, and potentially to connect that back to everything that person did elsewhere in Apple’s system.

Fix it, or opt out

If that’s not enough, many big advertisers also rely on extremely detailed data from third parties like LiveRamp and Experian. LiveRamp, for instance, can deliver clients huge volumes of data about everyday online transactions with only a single email address. And these companies can tell whether an ad displayed to an online user led to a purchase at a store.

“Google, Apple, and Microsoft, as the dominant operating system vendors, could easily fix this problem of cross-device user identification for advertising in a consistent, privacy-friendly way if they wanted to,” Litman said. “IDFA and Google AdID are steps in the right direction, and hopefully Apple and Google will continue to improve them and and create a standard that everyone can support.”

But it’s also crucial to remember that, whether you’re using an iOS or Android device, you are able to turn off most of the tracking mechanisms — the settings menus of both operating systems help you do this.

And for people who don’t want to be tracked by Atlas, Eyeo released an updated version of its popular AdBlock browser plug-in, AdBlock Plus, on October 1.

Correction: We’ve corrected the paragraph about iOS cookies. Apple’s Safari has always supported cookies. Some apps do use cookies, but they are not shared with the browser, and Apple has taken a dim view of user tracking with cookies.