Facebook launched a revolutionary cross-device ad system today that will inform advertisers where consumers saw an ad and which device they used to make a subsequent purchase.

"With the new cross-device report, advertisers are now able to see where someone saw an ad, the device they used, and which device was used when they converted," Facebook said in a statement quoted by Bloomberg News.

This marketing magic comes about through a tiny piece of code known as a "conversion pixel" that lets Facebook advertisers track users across multiple devices, Mashable reported.

"Tracking click and conversion data deterministically across devices has confirmed what we know to be true: mobile ads drive commerce everywhere," Josh McFarland, CEO of TellApart, a Facebook Preferred Marketing Developer, said in a blog post quoted by Mashable. "This new reporting from Facebook has been a game-changer in our ability to help clients like Neiman Marcus and Sur La Table correctly value and invest in their mobile ads efforts."

The new feature is intended to show marketers where users first see ads; for example, a Facebook user could view an ad through the site's mobile app and then purchase the item hours later on a PC. According to Facebook, 32 percent of consumers who appear interested in mobile ads purchase something on a desktop computer within a month.

Marketers have long been working toward more detailed analytics to target ads to Internet users, and the ability to distinguish between devices marks the next step.

"The ad industry as a whole is moving increasingly towards more sophisticated attribution modeling," Max Kalehoff, SVP of marketing at the digital ad firm SocialCode, as quoted by Mashable. "An advertiser can be much more effective if she has control over the frequency and placement of messaging to individual people using different devices."

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