TLDR
A preregistered field experiment found forcing users into Google AI Mode cut click-through to external websites by 18.8 percentage points. A separate study found AI Overviews, present on roughly 41 per cent of queries, cut outbound organic clicks by 39.8 per cent. Both findings carry direct consequences for Australian publishers measuring performance through session counts.
The experiment and what it measured
A preregistered field experiment enrolling 1,444 US Chrome users found that assigning participants to Google AI Mode cut click-through to external websites by 18.8 percentage points (95% CI:, 22.2pp to, 15.3pp; p<0.001), according to a study published 18 August 2026.[1] Of those enrolled, 1,100 made at least one search during the seven-day treatment period.[1]
The same experiment tested the opposite condition. Hiding both AI Overviews and AI Mode entirely raised external click-through by 8.8 percentage points (95% CI: 2.3pp to 15.3pp; p=0.008).[1] That 27.6-point spread between the two conditions is the clearest quantified signal yet of what AI features cost publishers per search session.
Site-level damage
When AI Mode was active, click-through to news sites fell 12.5 percentage points, Reddit dropped 21.2 points and Wikipedia lost 9.9 points.[1] For any publisher whose revenue model runs through referral traffic, a 12.5-point drop in click-through erases material ad inventory.
AI Mode also reduced daily search sessions by 0.92 per user (95% CI:, 1.30 to, 0.55; p<0.001) and lowered trust in information found on Google by 0.34 points on a 7-point scale.[1] Study authors Stephanie T. Wang et al. said integrating generative AI into web search reshapes online attention, with economic consequences for the online publishers that sustain both search platforms and the overall information ecosystem.[1]
AI Overviews: a separate study, a worse number
A parallel study by Agarwal and Sen examined AI Overviews specifically, the synthetic summaries Google embeds at the top of results pages.[2] Conditional on an AI Overview appearing, outbound organic clicks fell 39.8 per cent and zero-click searches rose 34.5 per cent, with no compensating increase in sponsored clicks or overall search frequency.[2]
Google has argued publicly that AI features surface deeper queries and create new traffic opportunities for websites. The Agarwal-Sen data finds no sponsored-click offset to replace the organic traffic lost when an Overview appears, so publishers absorb the full loss.[2]
What the numbers mean for measurement
Wang et al. said that removing AI Overviews and AI Mode increases click-through rates to publishers, while an AI Mode-only experience reduces click-through rates and erodes user experience and trust in information found on Google.[1] The study was preregistered, meaning the analysis plan was locked before data collection began between 17 and 19 March 2026, which reduces the risk of post-hoc result shopping.[1]
Australian publishers and agencies still measuring search performance through raw session counts will understate the scale of referral loss documented here.[3] Google launched AI Overviews in May 2024 and introduced AI Mode, a conversational interface powered by Gemini, in 2025. Both studies now quantify what the industry previously estimated only through traffic dashboards and anecdote. The Wang et al. paper carries a publication date of 18 August 2026.
KEY TAKEAWAYS
SOURCES & CITATIONS
FREQUENTLY ASKED QUESTIONS
What is Google AI Mode and how does it differ from AI Overviews?
Did AI Overviews increase sponsored or paid clicks to offset the drop in organic clicks?
How was the Wang et al. experiment designed?
Jonas Valenti writes about search and how businesses get discovered. He has spent years watching what makes a company visible online, and is unsentimental about tactics that no longer work.
