For decades, shoppers have taken advantage of coupons. Now, the coupons are taking advantage of the shoppers.

A new breed of coupon, printed from the Internet or sent to mobile phones, is packed with information about the customer who uses it. While the coupons look standard, their bar codes can be loaded with a startling amount of data, including identification about the customer, Internet address, Facebook page information and even the search terms the customer used to find the coupon in the first place.

And all that information follows that customer into the mall. For example, if a man walks into a Filene’s Basement to buy a suit for his wedding and shows a coupon he retrieved online, the company’s marketing agency can figure out whether he used the search terms “Hugo Boss suit” or “discount wedding clothes” to research his purchase (just don’t tell his fiancée).

Coupons from the Internet are the fastest-growing part of the coupon world — their redemption increased 263 percent to about 50 million coupons in 2009, according to the coupon-processing company Inmar. Using coupons to link Internet behavior with in-store shopping lets retailers figure out which ad slogans or online product promotions work best, how long someone waits between searching and shopping, even what offers a shopper will respond to or ignore.