Walmart last week reported rising sales of household items such as clothes, groceries and toys. But its profits rose faster thanks in part to a product that will not fit into a shopping cart: advertising.

The world’s biggest retailer has bought myriad ads in newspapers, on television and online in its 62-year history. Now, it is selling airtime to other advertisers, competing with traditional media companies for marketing dollars. 

Its US ad business, Walmart Connect, is part of an emerging industry known as “retail media”, in which big retailers flex their muscles as gatekeepers between vendors and consumers to sell ads to brands seeking an edge. US spending on retail media will exceed $54bn in 2024, Emarketer forecasts, up from $18.7bn in 2020.