On its website, the firm claims that advertisers who qualify to use its "store sales management" service can see whether an ad click or video view results in an in-store purchase within 30 days.
As part of the deal, when a Google user clicks on an online advert, their activity is recorded on a database, . Bloomberg says when you walk into a brick-and-mortar store to buy a pair of red stilettos using a Mastercard, Google will know and will report your purchase to the advertiser that ran that campaign as "offline revenue". That's why Google tracks your location all the time, even if you turn off location history.
The revelation has raised questions about how much data Google is quietly harvesting without user knowledge.
"People don't expect what they buy physically in a store to be linked to what they are buying online", said lawyer Christine Bannan at the advocacy group Electronic Privacy Information Centre.
According to Bloomberg, this deal was finally brokered between the two companies after four years of negotiation.
In a statement, Google said that it built a "new, double-blind encryption technology that prevents both Google and our partners from viewing our respective users' personally identifiable information".
Although Google has not commented on the partnership with Mastercard, it has commented on the tool used to share the data to help calm fears about privacy. That's not information the majority of people would be comfortable with Google having access to, let alone advertisers, especially when it was scraped from what should be a trusted source: your credit card company. Though Mastercard has been confirmed to be a part of that 70 percent metric, there are likely other financial service companies in the United States that have participated as well. The way this works is, a person clicks on an ad for something like red lipstick while they're logged into a Google account.
Last year, when Google announced the service - called Store Sales Measurement - the company said it had access to "approximately 70 percent" of US credit and debit cards through partners, without naming them.
"No individual transaction or personal data is provided", Eisen said in a statement. Next, the user browses a certain item and doesn't purchase it.