ChatGPT hits 1 billion monthly active users in record time

ChatGPT reached 1 billion global monthly active app users in May, becoming the fastest app ever to hit the milestone, according to market intelligence firm Sensor Tower. It got there roughly three years after launch, outpacing the adoption curves of Google Maps, TikTok, Instagram and YouTube — a striking demonstration of how thoroughly generative AI has gone mainstream.

The milestone is also a strategic flex ahead of OpenAI's expected IPO filing, paired with Codex expansion across the ChatGPT app, six business plugins, and the new 'Dreaming' memory system. OpenAI is leaning into consumer scale as its differentiator against more enterprise-focused rivals.

But the same Sensor Tower data complicates the triumphant headline. Anthropic's Claude app reached 56 million global MAUs with year-over-year growth of roughly 640%, dramatically outpacing ChatGPT's 62% growth. Sensor Tower also found U.S. ChatGPT users who installed Claude in Q1 2026 spent 5% less time on ChatGPT a month later — early evidence of real substitution at the margins.

The skeptical frame: raw MAU is a vanity metric if engagement and monetization lag, and PitchBook has flagged OpenAI as 'the worst value among its AI peers' heading into its listing. The number to watch isn't users — it's revenue per user and whether OpenAI can defend share as Claude, Gemini and free local models proliferate.