OpenAI’s ChatGPT has become the fastest app ever to reach one billion monthly users, crossing the mark in May, according to market intelligence firm Sensor Tower.
The app reached one billion monthly active users (MAU) roughly three years after its 2022 launch, outpacing Google Maps, TikTok, Instagram and YouTube, Sensor Tower said. The figure is an estimate of app usage and does not count people who use ChatGPT through the web or its developer tools.
The milestone lands amid sharpening competition between OpenAI and rival Anthropic, the maker of the Claude assistant. Sensor Tower put Claude at 56 million global monthly users in the current quarter, a far smaller base that grew about 640% from a year earlier. That pace ran well ahead of ChatGPT’s 62% growth over the same period.
The data also pointed to early signs of users moving between the two products. Sensor Tower estimated that United States ChatGPT users who installed Claude in the first quarter of 2026 spent 5% less time on ChatGPT a month later, measured against their average over the previous eight months.
Both companies are now edging toward public markets. Anthropic confidentially filed for a United States initial public offering (IPO) on Monday. Reuters has reported that OpenAI is preparing its own filing in the coming weeks.
The contrasting figures reflect two different strategies. ChatGPT leads the consumer mass market by a wide margin, while Claude is expanding quickly from a smaller base, with particular strength among developers and in coding.
