The Infinite Brief

For the past year, select Google advertisers have had access to a potent new tool to track whether the ads they ran online led to a sale at a physical store in the U.S. That insight came thanks in part to a stockpile of Mastercard transactions that Google paid for.

The alliance gave Google an unprecedented asset for measuring retail spending, part of the search giant’s strategy to fortify its primary business against onslaughts from Amazon.com Inc. and others.

Through this test program, Google can anonymously match these existing user profiles to purchases made in physical stores. The result is powerful: Google knows that people clicked on ads and can now tell advertisers that this activity led to actual store sales.