Similarweb put Claude at 9.6% of generative-AI website traffic in September 2026, up from 2.3% in October 2025, in its monthly traffic share update posted on X on 12 October 2026. On the same measure ChatGPTfell to 56.4% from 71.8%, and Gemini rose to 25.0% from 13.6%.
By our arithmetic, Claude’s share is a little over four times its level of a year earlier, and Gemini’s is about 1.8 times. Over the last six months the movement has been smaller and in the other direction for the two largest: Similarweb gives ChatGPT 53.7% and Gemini 26.7% in April 2026.
Business Pill · PROXY MEASURE
A one-minute explainer of the idea that a count is not the thing you care about: a measure such as visits can stand in for something else, such as usage or value, only up to a point. It teaches the general idea only and says nothing about any person or organisation in this story.
The key insight: As we read it, the year-on-year story and the six-month story point different ways. Against October 2025, ChatGPT’s share of generative-AI website traffic is 15.4 points lower and Claude’s and Gemini’s much higher; since April 2026, Similarweb’s figures show ChatGPT edging back up and Gemini edging down.
The update lists seven sites at five points in time: 12 months ago (October 2025), six months ago (April 2026), three months ago (July 2026), two months ago (August 2026) and one month ago (September 2026). Its chart is labelled “All Traffic” and “Worldwide”.
For September 2026 Similarweb gives ChatGPT 56.4%, Gemini 25.0%, Claude 9.6%, DeepSeek 3.4%, Grok 2.3%, Copilot 1.5% and Perplexity 0.9%.
For October 2025 it gives ChatGPT 71.8%, Gemini 13.6%, DeepSeek 4.1%, Grok 2.8%, Perplexity 2.5%, Claude 2.3% and Copilot 2.0%.
Share of generative-AI website traffic among the seven sites Similarweb lists, October 2025 against September 2026, as given in Similarweb’s update posted on X on 12 October 2026 (all traffic, worldwide).
What Was Posted on X
Gen AI website traffic share update – September 2026
Similarweb’s own post of 12 October 2026 with its gen-AI website traffic shares for September 2026 and four earlier periods. Every share in the piece comes from it; it covers website visits only.
A Year of Movement
By our arithmetic, ChatGPT’s share is 15.4 points lower than in October 2025, Gemini’s 11.4 points higher and Claude’s 7.3 points higher. Claude moved from sixth place among the seven sites listed in October 2025 to third in September 2026.
The smaller sites lost ground over the year in Similarweb’s figures: Perplexity fell from 2.5% to 0.9%, DeepSeek from 4.1% to 3.4%, Grok from 2.8% to 2.3% and Copilot from 2.0% to 1.5%.
ChatGPT, Gemini and Claude as a percent of generative-AI website traffic at the five points Similarweb gives (not evenly spaced), from its update posted on X on 12 October 2026.
The Last Six Months
The trend since April runs differently. Similarweb gives ChatGPT 53.7% in April, 54.3% in July, 55.6% in August and 56.4% in September. Gemini went from 26.7% in April to 26.6% in July, 25.6% in August and 25.0% in September.
Claude was at 8.0% in April, 9.6% in July, 9.3% in August and 9.6% in September. By our arithmetic, ChatGPT has added 2.7 points since April, Gemini has lost 1.7 points and Claude has gained 1.6 points.
The Structural Read
Similarweb’s update compares five dates rather than a continuous series in its text, so the shape between them comes only from the attached monthly chart, which we have not digitised.
As we read it, the largest single shift in the figures happened before April 2026: ChatGPT went from 71.8% in October 2025 to 53.7% in April, and Gemini from 13.6% to 26.7%.
Claude’s share has moved in a narrow band since July in Similarweb’s figures, at 9.6%, 9.3% and 9.6% for July, August and September.
Similarweb, X post of 12 October 2026
“Gen AI website traffic share update – September 2026”
Three Implications
READERS OF SHARE TABLES Similarweb’s figures are shares of website traffic among the sites it lists, not of apps, API calls or revenue, and the post does not set out its method.
COMPARISONS OVER TIME The update gives five points, October 2025, April, July, August and September 2026, so changes between them are differences between those points only.
THE SMALLER SITES In Similarweb’s figures Perplexity fell from 2.5% to 0.9% over the year, and DeepSeek, Grok and Copilot each lost share too.
The framework puts it this way: “The casual user pays $20 and uses 2% of capacity — they are the cross-subsidy”.
As we read it, a share of website visits counts the casual surface the framework describes; it says nothing on its own about which site holds the heavy users whose spending the framework treats as the asset.
What Is Not Established
Similarweb’s update measures website traffic share among the generative-AI sites it lists; it does not cover mobile apps, API usage or paying users, and the post we read does not describe its method. Shares of visits are not shares of revenue or of usage time. The update does not say why any site gained or lost share, and we have not attributed a cause.
Business Engineer Framework
The Subsidized AGI Economy
A Business Engineer framework on who pays for AI usage, which users subsidise which, and where the economics break.
Similarweb’s September 2026 figures put Claude at 9.6% of generative-AI website traffic, from 2.3% a year earlier, and Gemini at 25.0%, from 13.6%, while ChatGPT fell to 56.4% from 71.8%. Since April, ChatGPT’s share has edged up and Gemini’s has edged down.
A note on sourcing. On 12 October 2026 we read in full Similarweb’s generative-AI website traffic share update, posted on its own X account that day, and looked at the chart attached to it; every share here comes from it. Similarweb’s figures are estimates of website traffic among the sites it lists, and the post does not set out its method. Ratios and differences are our arithmetic. Nothing here is a forecast or investment advice.
Gennaro Cuofano is a CRO and tech executive who has worked in AI since late 2015, starting with bringing NLP, natural-language generation, voice and chatbot products to the marketing industry. His background is in law and finance: he holds a Master's degree in Law and an International MBA with an emphasis on corporate finance (LUISS Business School and the University of San Diego, 2012), and worked as a financial analyst at a real-estate investment firm in San Diego and as an assistant controller. His work focuses on business model strategy, business engineering and, more broadly, structural analysis: how companies make money, read from their own filings. He created FourWeekMBA and leads research there and at The Business Engineer, his newsletter on AI and business strategy, with over 95,000 subscribers and more than 1,000 published analyses. His writing has also appeared on Entrepreneur, HackerNoon and Search Engine People. Find him on LinkedIn and Substack. See how we source.
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