AdRoll, Dentsu, Omnicom test ChatGPT ad buying as Gartner sees 70% shift by 2028

August 17, 2026 · marketingreport.one

More than 70% of global advertising spend will move through AI-influenced self-service platforms by 2028, according to Gartner, as ChatGPT becomes a testing ground for a new buying mechanic. AdRoll is piloting advertising placements directly inside ChatGPT, and Dentsu is pairing ChatGPT campaigns with competitive intelligence from Adthena. Omnicom Media has gone further, testing autonomous AI agents that identify inventory, negotiate terms and complete ad purchases on their own.

Consumers increasingly research and compare products inside ChatGPT itself, giving brands a chance to shape preferences before a purchase search even begins on a traditional platform. Media planning shifts toward writing briefs for AI systems that determine which ads appear, who sees them and what advertisers pay, and agency value concentrates in strategy, data and oversight of these systems. Independent measurement and transparency become essential checks as machines take on greater control over targeting, pricing and placement.