OpenAI’s ChatGPT has crossed 1 billion monthly active users worldwide, and it did so faster than any other app in history, according to Sensor Tower estimates. The milestone arrived about three years after launch, putting it ahead of the usual consumer-app heavyweights such as Google Maps, TikTok, Instagram, and YouTube. But the bigger story is that Anthropic’s Claude is growing much faster right now, even if it is starting from a much smaller base.
That split tells you a lot about the current AI race: ChatGPT is the default destination, while Claude is still the faster riser. In app markets, the winner is often the one that turns usage into habit first, but the challenger can still win mindshare by moving quicker on growth and retention. OpenAI has scale; Anthropic has momentum.
ChatGPT’s record run to 1 billion users
Sensor Tower’s estimate places ChatGPT in rare company, except this time the company is a lot larger and a lot more crowded. Reaching 1 billion monthly active users in roughly three years makes ChatGPT the fastest app ever to that mark, which is an awkward result for every other AI firm trying to sell itself as the next unavoidable platform.
- ChatGPT monthly active users: 1 billion worldwide
- Time to hit the milestone: about three years after launch
- Previous apps it outpaced: Google Maps, TikTok, Instagram, and YouTube
Claude is taking more share from heavy users
Anthropic’s Claude isn’t close to ChatGPT’s scale, but it is posting the kind of growth rate that makes product teams sit up. Sensor Tower said Claude had 56 million monthly active users worldwide in the current second quarter, and that figure was up about 640% year on year. ChatGPT’s growth was 62% over the same period, which is still enormous, just less absurd.
There is also a usage-quality wrinkle here. Sensor Tower said U.S. users who installed Claude in the first quarter of 2026 spent 5% less time in ChatGPT one month later than the average of the previous eight months. That does not prove a full-blown switching wave, but it does suggest Claude is nibbling at attention where it matters most: among people already willing to use AI every day.
IPO plans add pressure to both companies
The timing is convenient, and not by accident. Anthropic filed confidentially for a U.S. IPO on Monday, while Reuters reported that OpenAI is also preparing to file in the coming weeks. Public-market scrutiny will force both companies to explain the same awkward question: is the AI boom about engagement that keeps rising, or about monetization that can keep up?
For now, OpenAI owns the headline number. Anthropic owns the faster growth curve. The next fight is not over who has the biggest app, but who can keep users from drifting once the novelty wears off.