ChatGPT surpassed the milestone of one billion monthly active users in May, three years after its launch. No other app in history has reached this figure faster. Not TikTok, Instagram, or YouTube. Yet OpenAI cannot completely relax, because Anthropic and its chatbot Claude are growing at an unprecedented pace.
The analysis was published by the news agency Reuters, based on data from Sensor Tower, which tracks user activity on mobile platforms. By comparison, Instagram took more than ten years. TikTok reached similar figures in approximately six years, while ChatGPT managed it in three. At the beginning of the year, OpenAI announced 900 million weekly active users. So these are not people who downloaded the app once and forgot about it. This reflects everyday use at work, school, and elsewhere.
Claude is growing even faster
However, one thing is causing concern among OpenAI executives. Anthropic's Claude model has 56 million monthly active users during the second quarter. That is a fraction of ChatGPT's user base. But Claude's year-over-year growth stands at 640 percent. ChatGPT grew by 62 percent over the same period. These figures need to be viewed in context. Claude is starting from a lower base, so such an increase is mathematically easier to achieve. But that does not make it insignificant. On the contrary, Anthropic is establishing its position at a pace that OpenAI did not achieve in the early stages of its growth.
Sensor Tower also reported a specific finding: U.S. ChatGPT users who downloaded the Claude app in the first quarter of 2026 spent 5 percent less time on ChatGPT just one month after installing it, compared with the previous eight months. Five percent may not sound dramatic, but it is the first visible sign that users have not started using Claude merely as a supplementary tool. Some have begun to prefer it.
Users are one thing; money is another. And OpenAI can boast 50 million paying subscribers. That is a figure that tells every investor the business model works. People not only use ChatGPT, but are willing to pay for it. Anthropic does not yet have a paying customer base on that scale, but it is pursuing corporate clients all the more aggressively. And that is precisely where the real battle for the market is taking place—in enterprise contracts and integrations.
