ChatGPT accounted for 81.2 per cent of September sessions across six AI services tracked in the new Graphite study using Similarweb data. Its share rose from June as total activity expanded. Website visits and mobile-app sessions form the calculation, with mobile devices carrying most activity. The figures describe the named services and measured surfaces rather than every use of artificial intelligence.
ChatGPT took 81.2 per cent of September activity across six services in Graphite’s study published on 9 November. The AI growth firm used Similarweb traffic estimates to combine website visits with mobile-app sessions. Its sample covers ChatGPT, Gemini, Claude, Grok, Perplexity and DeepSeek. ChatGPT’s share of tracked worldwide sessions rose by about 0.8 percentage points from June to September. The unit is a session, rather than a distinct person.[1], [2]
The six services totalled 76 billion sessions worldwide in September and 6.6 billion in the United States, increases of 37 per cent and 45 per cent from a year earlier. ChatGPT supplied 58.9 per cent of added worldwide sessions, compared with Claude’s 26 per cent and Gemini’s 12 per cent. Claude grew faster in proportional terms, while Perplexity’s worldwide sessions fell 27 per cent over the same annual comparison.[1]
Mobile applications provided 86 per cent of worldwide sessions; mobile web brought the mobile-device share to 89 per cent. The corresponding US shares were 74 per cent and 78 per cent. Reliable desktop-app data were unavailable, leaving that activity undercounted. Graphite also revised its earlier search comparison after finding that Google’s Android application had been incompletely counted. Its updated study avoids a total-size comparison between AI services and search.[1]
