The pitch to marketers for the last three years has been diversification. Stop funneling every dollar to Google and Meta, the thinking went, and put some of it into retail media instead: ads placed directly on Amazon, Walmart, Target, and dozens of other retailer sites, next to the products people are already shopping for. eMarketer forecasts US retail media spend will hit 69.33 billion dollars in 2026, up from 58.79 billion in 2025. On paper, that looks like real budget migration away from the two biggest players in digital advertising.
The money tells a narrower story. Of the roughly 10.53 billion dollars in new retail media spending expected in 2026, eMarketer projects 9.42 billion of it, about 89 percent, goes to just two companies: Amazon and Walmart. A separate eMarketer breakdown puts Amazon and Walmart’s combined share of total US retail media ad spend at 84.2 percent. Marketers did not leave a duopoly. They funded a new one, and it formed faster than the one they were trying to escape.
That pattern is not unique to retail media, it is the whole market’s shape now. The IAB and PwC’s Internet Advertising Revenue Report for full year 2025 found that the top 10 US ad sellers captured 84.1 percent of all internet advertising revenue, up from 80.8 percent in 2024, 79.8 percent in 2023, and 76.8 percent in 2022. Three companies, Alphabet’s Google, Meta, and Amazon, accounted for 56 percent of the 294.6 billion dollars in total US digital ad revenue the report counted for 2025. Search still led all formats at 114.2 billion dollars, with social close behind at 117.7 billion and growing 32.6 percent year over year. Every channel marketers have turned to for relief from concentration has concentrated at roughly the same rate.
Buyers also can’t fully verify what they’re getting for the money. At the IAB’s Connected Commerce Summit, 62 percent of retail media buyers surveyed cited a lack of consistent measurement standards as a major barrier to spending more. The IAB’s own commerce media research put it bluntly: the market cannot sustain hundreds of undifferentiated commerce media networks, a signal that the smaller retail media players marketers were counting on as real alternatives are the ones most likely to get squeezed out first, leaving the two biggest names even more dominant.
For budget planning, the practical read is to stop treating channel diversification as risk diversification. Spreading spend across search, social, and retail media does not reduce dependence on a small number of companies if the same two or three names sit at the top of every channel. Teams that want real negotiating power should weight retail media tests toward the networks outside the Amazon and Walmart tier, demand comparable measurement before committing larger budgets, and treat any “new channel” pitch with the assumption that it consolidates on the same timeline as the last one, not a longer one.
Sources referenced in reporting: