'OpenAI vs Google': ChatGPT traffic down 21% over six weeks as Gemini stays flat, says Similarweb

ChatGPT, the flagship generative AI product from OpenAI, is showing signs of slowing momentum as Google’s Gemini continues to narrow the gap, according to fresh traffic and market-share data from Similarweb.

Data reviewed by Similarweb shows that ChatGPT’s average daily visits have fallen sharply over the past six weeks. Traffic declined by about 22%, with the seven-day average dropping from roughly 203 million visits to around 158 million by early January. Over the same period, Google’s Gemini held steady, recording about 55-60 million daily visits.

The shift has translated into a measurable change in market share. ChatGPT’s share of the global generative AI market stood at about 64.5% as of January 2, 2026, down from around 68% in December 2025 and sharply lower than its 86% share a year ago in January 2025. Gemini, meanwhile, has expanded its footprint significantly, growing from 5.7% a year ago to approximately 21.5% now.

Other platforms remain smaller but are gaining traction. Grok has crossed the 3% market share mark and is closing in on DeepSeek, which stands at about 3.7%. Perplexity and Claude are each holding steady at around 2%, while Microsoft’s Copilot trails at roughly 1.1% in January 2026, showing little change over the past year.

While ChatGPT continues to lead in overall traffic, the data suggests its growth curve has flattened. Similarweb estimates that Gemini cannibalised around 31-33% of ChatGPT’s traffic in early December, with that figure rising to nearly 39-40% by the end of the month.

User behaviour also differs between the two platforms. Gemini appears to attract fewer users, but engagement levels are higher. Average session duration on Gemini stands at 7 minutes and 20 seconds, compared with 6 minutes and 32 seconds on ChatGPT. Page views per visit are also higher on Gemini, at 4.3 pages, versus 3.8 on ChatGPT.