OpenAI’s ChatGPT reached an estimated 1 billion monthly active app users worldwide in May, about three years after launch, becoming the fastest app to hit that mark, according to market intelligence firm Sensor Tower.

Sensor Tower said ChatGPT grew faster than Google Maps, TikTok, Instagram, and YouTube. It added that Anthropic‘s Claude app had 56 million monthly active users worldwide in the second quarter to date, while its year-on-year monthly active user growth of about 640% outpaced ChatGPT’s 62%.

The firm also said ChatGPT users in the US who installed Claude in the first quarter of 2026 spent 5% less time on ChatGPT one month later, compared with their average usage over the previous eight months.

Anthropic filed confidentially for an initial public offering in the US on Monday, while OpenAI was preparing to file in the coming weeks.

Sensor Tower’s active-user estimates are derived from a global consumer panel, app store application programming interfaces, models, and third-party datasets.

Its usage products focus on mobile app engagement, which suggests the 1 billion figure reflects app activity rather than web usage.

🔗 Source: Reuters

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