What is a retail media network, and why is every retailer building one?
A retailer selling advertising inventory against its own shopper data — on its website, in its app, in physical stores, and increasingly on other websites entirely. It has become the fastest-growing advertising category, and the reason is margin.
Why retailers want one. Retail is a low-margin business; advertising is a very high-margin one. A retailer already has the two things advertisers most want — purchase data and shoppers in a buying mindset — and selling access to them adds profit without adding stock, warehousing or delivery. For several large retailers, media revenue now contributes a disproportionate share of total operating profit.
Why advertisers want it, and this is the substantive part:
Closed-loop measurement. The retailer sees both the ad exposure and the purchase, in its own data, without needing third-party cookies or cross-site tracking. In an era of signal loss, that is a genuinely rare capability.
Actual purchase history rather than inferred interest — the difference between someone who bought nappies and someone who read about them.
Proximity to the transaction. A search on a retailer's site is a shopper with intent, one click from checkout.
Incrementality is the honest problem. Much retail media spend targets people already about to buy — someone searching for your brand by name on a retailer's site was probably going to purchase it. Attributed return on ad spend looks spectacular and can be substantially cannibalised rather than incremental. Serious advertisers run holdout tests rather than trusting the platform's own attribution.
The other tensions:
The retailer marks its own homework, reporting on the campaigns it sells.
Pay-to-play pressure, where media spend becomes an effective condition of shelf and listing negotiations.
Competition for attention with the shopping experience itself.
Off-site extension — retailers selling their data for targeting elsewhere — is where growth now concentrates, and it reintroduces the measurement problems on-site retail media avoided.