Advertisers can now see if their Amazon ads drive sales at Walmart, Best Buy, and Target. Does that give them an edge?

Amazon is, of course, the biggest e-tailer in the world—and, with Prime Video, it’s also one of the biggest streaming services. And since it started running ads on Prime Video content for all viewers last year, it also has an ever-expanding amount of digital ad inventory for marketers who want to run commercials alongside the originals it pays hundreds of millions of dollars to produce.

Amazon can tell those marketers if their ads drive sales on its platform. What it doesn’t do, however, is tell them whether their ads drive sales from retail giants like Walmart and Target. That info is traditionally available only to the retail giants themselves, kept in their “walled gardens” of data.

But retail media tech companies Stackline and Gigi have now signed a partnership to access it—and share it with marketers.

Per Adweek, Gigi is a startup that helps brands place TV ads on Amazon-, Disney-, and NBCUniversal-owned streaming services, then provides performance data. Stackline, meanwhile, collects first-party personal data from one million+ people who’ve opted in to having their in-store and online shopping tracked by Amazon, Walmart, Target, and Best Buy.

Adweek reports these one million people spend about $10 billion annually.

While this sample obviously covers just a fraction of Amazon’s 200 million Prime subscribers, it’s statistically significant enough to show brands what sort of behavior Prime viewers exhibit. The point of Stackline and Gigi’s partnership is to help marketers draw clearer lines between Prime Video ads and retail sales.

Why is that such a pressing concern? Because analysts like eMarketer forecast that brands will spend $60 billion this year on “retail media”–that is, digital ads aimed at encouraging people to buy from brick-and-mortar retailers rather than ecommerce platforms.

Gigi co-founder/CEO Adam Epstein told Adweek that brands can use it and Stackline’s data to create ads that, for example, target someone who shops at Walmart every week but watches Amazon video content. A brand leaning hard into Walmart sales might not know about that person without access to this data—but after knowing, could create ads specifically encouraging them to look out for its product next time they’re in the store. (That’s a big difference from a lot of digital advertising, which often has call-to-actions that encourage viewers to buy right now immediately

Greg Wolny, Stackline’s VP of Marketing, told Adweek he thinks this will lead to brands fine-tuning their current Amazon marketing, and maybe even buying more, since Stackline and Gigi are targeting marketers that currently spend big on traditional TV ads.

So far, “We’re seeing it impact overall [digital] allocation,” he said. “It’s not necessarily taking away from Amazon—in this case, Amazon is so robust.”

Zach Servideo, CEO at consulting firm Value Creation Labs, tells Tubefilter that “if Stackline and Gigi can do what they claim, they’re stitching together a retail media network that gives marketers conversion metrics across walled gardens.

“That’s impressive,” he says. “It reminds me of what Seattle-based ad tech Downstream Impact was striving toward in the late 2010s leading to their massive exit to Jungle Scout via Summit Partners in 2021. They were founded by former Amazon ads employees that were white-knighted into the Amazon ads ecosystem to build targeting and performance measurement tools–and yes, this included point of sale metrics mapping impressions to conversions.”

So, brands could have an edge by signing on with Stackline and Gigi. But Servideo thinks the business model here could also have wider implications.

“I’d also be on the lookout for how YouTube might benefit from all this,” he said. “If the biggest video advertising player globally can plug into conversion metrics across retailer walled gardens, it may be game over for the rest of media playing in the attention economy, if it isn’t already.”