ChatGPT crosses 1 billion monthly users as Claude eats into user engagement

ChatGPT crossed 1 billion global monthly active users in May, becoming the fastest application ever to reach that number, according to Sensor Tower. It hit the milestone roughly three years after launch, outpacing Google Maps, TikTok, Instagram, and YouTube.

The milestone comes at a time when both OpenAI and Anthropic are gearing up for their IPOs, with Anthropic having filed confidentially for its U.S. IPO on Monday, according to Reuters, with OpenAI set to follow suit soon.

ChatGPT moved from saturation in Q4 2025 to a billion users

As Cryptopolitan observed in December, monthly active users of ChatGPT globally increased only by 6% from August to November 2025 to reach 810 million, a growth rate that implied that ChatGPT had almost become saturated.

Gemini’s users rose 30% over the same stretch. The slow climb was significant enough that OpenAI CEO Sam Altman issued an internal “code red” memo directing staff to improve personalization, reliability, and image generation.

The 1 billion milestone shows the ceiling was higher than the December data implied. ChatGPT added roughly 190 million monthly app users in about six months after the saturation warning.

Claude sees more engagement as ChatGPT usage dips

As per reports by Sensor Tower, users of ChatGPT in the US who downloaded Claude in the first quarter of 2026 spent 5% less time using ChatGPT one month later as compared to their usage in the last eight months.

The user base of Claude stands much lower than that of ChatGPT, being only 56 million global monthly active app users until Q2 2026. On a yearly basis, however, the MAU growth rate of Claude outshines that of ChatGPT by standing at 640%, against the latter’s modest growth rate of 62%.

Users are not leaving ChatGPT, rather are splitting their time between ChatGPT and Claude.

That tracks with where prediction-market money is sitting. On Polymarket, traders price Anthropic at roughly 84% to have the best AI model by the end of June, ahead of both Google, xAI and OpenAI.

Anthropic released Claude Opus 4.8 last week and said Mythos-class models will be available to all customers in the coming weeks. Cryptopolitan reported that Opus 4.8 outperformed GPT-5.5 on at least 12 benchmarks covering knowledge work, agentic tool use, and long-context tasks.

Anthropic filed for its IPO a day before the milestone

Anthropic filed confidentially for a US initial public offering on Monday, June 1, a day before the ChatGPT data landed. Reports say OpenAI is preparing to file its own confidential prospectus with Goldman Sachs and Morgan Stanley in the coming weeks, targeting a potential debut later in 2026.

At the time of writing, Polymarket traders give Anthropic a 74% probability of listing before OpenAI.

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