Kroger is launching a private programmatic marketplace for brands to reach its shoppers on the open web using the retailer’s first-party purchase data and IDs, then track resuls and optimize creative and targeting based on sales impact.

Kroger’s marketplace will let brands use demand-side platforms of their choice, either their own or third-party providers, a departure from some other retailer offerings, notably the marketplace Walmart is launching this month in partnership with The Trade Desk.

Cara Pratt, senior VP of Kroger Precision Marketing, announced the launch during a session at Advertising Week New York on Wednesday, alongside executives from Publicis Groupe and its Spark Foundry agency, who were “alpha testers” of the platform.

Nestle Coffee Partners was a beta tester. And in a prepared statement during the presentation, Kathi Christensen, senior brand manager for Nestle’s Starbucks packaged coffee business, praised Kroger Private Marketplace for its “ability to link our advertising to metrics that matter to us, including household penetration, incremental sales lift, and the ability to attract new buyers who are switching.”

Kroger serves 60 million households nationwide through its flagship nameplate and others such as Ralphs, Fred Meyer and Harris Teeter. Pratt said the platform was built to give agencies flexibility to target based on individual campaign objectives. The self-service platform also lets users customize based on their own brand-safety criteria.

The growing importance of first-party retail data amid the impending death of third-party cookies and other individual identifiers is obvious from the makeup of Advertising Week presenters, Pratt said.

“Is it any surprise that five of the top 10 U.S. retailers are on stages here at Advertising Week?” she asked. “As media sellers, retailers have the ingredients to make brand advertising more effective.”

Loyalty data like Kroger is providing “allows us to really understand why consumers are buying things and are we driving incrementality,” said Amy Lanzi, commerce practice lead at North America Publicis Groupe. “That’s very different versus other purchase data.” Shopper card data also allows advertisers to track both online and in-store sales effects from their campaigns, she noted.

Packaged-goods marketers are trying to build their own first-party databases, but find the experience “clunky,” given that they sell so few of their products direct to consumers, said Amanda Mollet, senior VP at Spark. KPM, besides providing a direct view of shoppers, provides almost instant feedback on campaign impact, Mollet said. “You don’t have to wait for that latency” of marketing-mix modeling “to tell you that the media is working.”