Amazon.com is the undisputed ruler of retail media, taking up 40 percent of total ad spend in the category with an 18 percent year-over-year growth in its ad revenue in 2024. Big-box retailers like Walmart, Target, and Best Buy, along with top grocers including Albertsons and Kroger, have captured meaningful ad dollars with their retail media businesses, leading to many more retailers (and nonretailers) jumping in with nascent offerings of their own.