Retail Media Networks: Why They're Eating Ad Budgets

Retail media is the fastest-growing channel in advertising. Here's what retail media networks are, why retailers and brands love them, where they fit in a plan, and how to avoid overspending.

By MediaPlan · 9 min read

Retail media is the fastest-growing channel in advertising, and it's not close. What started as sponsored product listings on a few large retailers has become a multi-hundred-billion-dollar category that nearly every retailer now wants a piece of. For planners, retail media networks (RMNs) are impossible to ignore — and easy to overspend on if you don't understand what you're actually buying.

What a Retail Media Network Is

A retail media network is an advertising business run by a retailer, using its own first-party shopper data and digital real estate to sell ads. When you buy retail media, you're typically buying some mix of:

On-site ads — sponsored product listings, banners, and search results on the retailer's website or app.
Off-site ads — display, video, and social placements the retailer targets using its shopper data but serves elsewhere across the web.
In-store — increasingly, digital screens, audio, and connected experiences inside physical stores.

The retailer is both the media owner and the data owner — and, crucially, the place where the purchase happens.

Why Retail Media Is Exploding

Three forces converged to make RMNs the industry's growth engine:

First-party purchase data. As third-party cookies and tracking erode, retailers sit on something rare and durable: logged-in, real purchase behavior. That's the highest-intent data in advertising.
A closed loop to the sale. Because the ad and the transaction live in the same place, RMNs can tie ad exposure directly to purchases — closed-loop measurement other channels can only approximate.
High-margin revenue for retailers. Retail is a thin-margin business; advertising is not. Media revenue drops almost straight to the bottom line, so every retailer is racing to launch a network.

Retail media's superpower is proximity to the purchase. You're not reaching a shopper near the top of the funnel — you're reaching them with their hand on the digital shelf.

Where Retail Media Fits in a Plan

Most retail media is lower-funnel, high-intent demand harvesting — closer to paid search than to CTV. On-site sponsored listings reach people who are already shopping the category, at the moment of decision. That makes RMNs powerful for conversion and for winning share at the shelf, but it also means they don't create demand on their own.

The off-site piece is where retail media stretches up the funnel: using purchase data to target audiences across the open web and social, then closing the loop back to sales. That's valuable, but it competes with the rest of your awareness and consideration budget and should be judged on incremental sales, not just attributed ROAS.

The Overspending Traps

Retail media's closed-loop measurement is a double-edged sword. A few cautions:

Attributed ROAS flatters retail media. Because the network measures the conversion happening on its own site, it naturally claims credit — including for purchases that would have happened anyway. Push for incrementality, not just reported ROAS.
The "tax" framing is real. For brands that sell through a retailer, retail media spend can drift from "advertising" into a cost of doing business with that retailer. Decide deliberately how much is true incremental media versus trade spend.
Fragmentation. Every retailer has its own network, console, ad formats, and measurement. Running ten RMNs means ten logins, ten taxonomies, and no clean cross-retailer view. Prioritize the few that match where your buyers actually shop.
Defensive spending. It's easy to fund sponsored listings just to keep a competitor off your product page. Sometimes worth it — but name it as defense, and cap it.

How to Buy Retail Media Well

Start where your category sells. Concentrate on the one or two retailers that own your shoppers, rather than spreading thin across every network.
Separate harvest from growth. Treat on-site search/listings as demand harvesting and judge them on efficiency; treat off-site as audience extension and judge it on incrementality.
Demand incrementality testing. Use holdouts or geo tests to learn what retail media truly added beyond attributed ROAS.
Coordinate with the funnel. Retail media converts the demand your awareness channels create. Fund the top of the funnel, or you'll be harvesting an ever-shrinking pool.

The Bottom Line

Retail media networks earned their explosive growth honestly: they pair the highest-intent first-party data in advertising with a direct line to the purchase. That makes them a potent lower-funnel and conversion channel — and a tempting place to overspend, because their own measurement always makes them look good. Concentrate on the retailers that matter, separate true incremental media from trade spend, insist on incrementality over attributed ROAS, and keep retail media connected to the demand-creating channels upstream. Do that, and the fastest-growing channel in advertising becomes one of the most accountable lines in your plan.