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Twitter's 'tailored ads' know more about you

The information network is letting advertisers use browser cookie data and customer databases to retarget prospects with promoted tweets.

Twitter CEO Dick Costolo.
Asa Mathat/D: All Things Digital

Twitter will soon show its U.S. users ads based on the Web sites they've previously visited.

Wednesday, the information network formally announced that it is experimenting with a new ad type it calls "tailored ads." With the units, advertisers can upload browser cookie IDs or email databases to push their promoted messages to people who have already shown interest in a particular brand or business.

"Users won't see more ads on Twitter, but they may see better ones," Kevin Weil, senior director of product revenue, said in a blog post.

The practice of targeting ads to people based on their browser history, also known as retargeting, is fairly common in digital advertising. Facebook's FBX ad exchange lets advertisers serve retargeted messages to people in the News Feed.

"Let's say a local florist wants to advertise a Valentine's Day special on Twitter. They'd prefer to show their ad to flower enthusiasts who frequent their website or subscribe to their newsletter," Weil explained. "To get the special offer to those people who are also on Twitter, the shop may share with us a scrambled, unreadable email address (a hash) or browser-related information (a browser cookie ID). We can then match that information to accounts in order to show them a Promoted Tweet with the Valentine's Day deal."

Though widespread, retargeted ads are eerily aware, and even Twitter's fluffy and sweet florist example, likely meant to assuage user fears, carries the reminder that you're always being watched on the Web.

Twitter users can, however, opt out of seeing these type of ads from their account settings, and those who have enabled "Do Not Track" in their browsers won't receive the browser-based ad units, the company said. Both decisions were applauded by the online privacy advocates at the Electronic Frontier Foundation.