Which AI tool is the most popular? It depends on what you count, and the four measures we pulled for October 2026 don't agree. Start with US Google searches. ChatGPT sat at about 124,000,000 a month in September 2026, the same as a year earlier. Canva and Gemini tied for second at 30,400,000, though most Canva searches are for the design tool and not its AI. Claude came next at 9,140,000, up from about 1,220,000 in October 2025, so more than seven times higher. And Janitor AI, a character-chat app, drew 4,090,000, which is more than Perplexity, DeepSeek and NotebookLM put together. That one surprised us.
Searching is not the same as using. To see who really opens a tool we went to Similarweb for site visits, Sensor Tower for app users and Statcounter for referrals, meaning the visits an AI tool sends on to other websites. ChatGPT took 52.7% of AI chatbot visits and 46.4% of app users in May 2026, and in September it sent 80.48% of the AI referral traffic that reached websites. Gemini was second each time, with 27.3% of visits, 27.7% of app users and 10.91% of referrals. Claude had 8.9% of visits and 10.3% of app users, yet only 0.95% of referrals.
Falling searches can hide growing use. Perplexity's US searches dropped 55% over the year, but its monthly app users went up 94%, according to Similarweb's 2026 generative AI report. ChatGPT's searches stayed flat while its app users rose 87%. DeepSeek and Microsoft 365 Copilot were the only two that fell on both counts.
Browser extensions add a third view. Grammarly had 40,000,000 users in the Chrome Web Store on October 19, 2026. That is eight times the next AI extension, Sider, with 5,000,000. The store rounds its numbers, so read them as minimums. Grammarly's searches fell by a third and it still sits in 40 million browsers, which makes sense: once something is installed and working, nobody has to search for it.
Developers are a fourth group and hardly appear in search at all. On OpenRouter, a service that routes developers to different AI models, Claude Code led usage.
Put together, ChatGPT leads search by about four to one, Grammarly leads browser extensions, and Claude Code leads developer usage. These come from different months and different sources, so treat them as a pattern. RankControl, an AI SEO and AEO platform, pulled the numbers. RankControl's AI visibility tracker tracks citations across 7 AI engines. The full numbers are in the full write-up on Medium.