Google and ChatGPT: shared audience, fewer clicks

95% of ChatGPT users still visit Google, according to Similarweb data covering September 2025 through May 2026. Visits to AI services grew 70% year over year while that overlap stayed flat. In other words, AI is not taking people away from search — it is being added on top.

The catch is that "the same people" does not mean "the same behaviour". A Bocconi University study on Comscore clickstream data found that households gaining access to ChatGPT Search cut traditional search queries by 9.4% — about 3.14 fewer per week — with the decline reaching 17% after 20 weeks. Informational categories took the hardest hit: academic sites −32.8%, reference −26.5%, developer resources −15.1%, news −13.4%. Google's household reach, meanwhile, held steady at roughly 49%.

A field experiment by Wang and co-authors looks harsher still: 1,100 Chrome users were pushed into AI Mode for a week, and external clicks dropped 18.8 percentage points, sessions fell by 0.92 per day, while each session ran longer. News sites lost 12.5 points, Reddit 21.2, Wikipedia 9.9. Matt Southern lined up all four studies at Search Engine Journal, adding a Pew survey (February 2026, 5,119 respondents) in which 60% read AI summaries directly in the results.

What not to confuse:

• audience overlap counts people, query studies count searches, clickstreams count visits to sites — three different metrics;
• Sundar Pichai says that "when people use our AI-powered features in Search, they use Search more", but Google offers no user-level verification;
• the drop hits informational content far harder than commercial content.

The practical read for a site owner is blunt: organic traffic to reference material is not coming back to previous levels. What deserves tracking now is the share of queries where you get cited and the revenue the remaining traffic produces.