Though the "Triopoly" of digital ad giants (Amazon, Google, and Meta) continues to rule the online space, their market share of US digital ad spend has recently experienced a decline.

While the dip isn’t massive, it exposes trends in digital media, including AI transformation and the growth of retail media, that reveal how digital ad spending will evolve over the next few years.

“[The Triopoly is] still around 60% share,” said our analyst Yory Wurmser, in a recent Behind the Numbers podcast. "Completely interesting and valid that the numbers are going down a bit, but at the same time, just want to point out that we don't want to overstate it as well."

Understanding the dip

Over the last five years, Amazon, Google and Meta have increased their share of total US ad spend from 47% in 2020 up to 59% in 2025, according to a July 2025 EMARKETER forecast. But within US digital media, the Triopoly’s share has declined from 73.9% to 71.9% over the same period.

“What we're seeing here, which is quite interesting, is that their share of total ad spend is rising,” said our analyst Eleni Digalaki on the podcast. “It's only increasing because digital is increasing as a whole. So they're riding that digital wave, but they're not actually gaining ground within digital. In fact, their grip on digital is slipping.”

Google’s and Meta’s market share shift is more noticeable with Amazon out of the equation, analysts say.

“Amazon has been riding the retail media wave over that [2020-2025] period,” said Digalaki. “Google and Meta have seen their share drop by roughly six percentage points over the last five years, so I think that's quite an interesting number.”

A fourth pillar

Other digital platforms, such as those in retail, video, and social media, make up a fourth pillar of rising stars. However, there is no single platform that can challenge the Triopoly's digital ad spending dominance.

“​​There are a lot of fast-growing channels [in digital advertising] and platforms across connected TV, retail media and social,” Digalaki said. “So the likes of Walmart, TikTok, Reddit, Peacock are some of those platforms that have been growing the fastest over that period.”

Walmart's US ad revenues are expected to surge by 44.1% this year, according to a September 2025 EMARKETER forecast. And we forecast that Reddit's US ad revenues will grow by 55.6% this year.

AI to the rescue

The final word has yet to be written on the long-term fate of the Triopoly. Each giant has its own challenges, but also opportunities to continue reigning in the digital realm, especially with AI and agentic commerce.

“Meta, Amazon and Google are all pretty well-positioned to grow in the AI era,” said Wurmser. “Google is probably the most threatened, just with search, but it also has some of the best AI technology out there, so it might actually ride the wave and do pretty well.”

And analysts believe that Google has room to grow with YouTube.

"I think Google has shifted its attention to YouTube," said Wurmser. "As YouTube figures out how to monetize the longer form TV, as well as targeting better with new ad formats, new shoppable ad formats within YouTube in all of its content, I think that that should drive up the ad revenues."

Listen to the full episode.