OpenAI’s ChatGPT has achieved a significant milestone by surpassing one billion global monthly active users, becoming the fastest application to achieve this feat, as reported by market intelligence firm Sensor Tower. This milestone was reached in May, approximately three years after its launch, indicating faster growth compared to popular apps like Google Maps, TikTok, Instagram, and YouTube, according to Sensor Tower.
The competition between OpenAI and rival Anthropic is escalating. Data from Sensor Tower reveals that users in the US who adopted Anthropic’s Claude app in the first quarter of 2026 spent 5% less time on ChatGPT a month later, compared to their average usage over the previous eight months. This suggests that Claude is starting to gain traction, although ChatGPT maintains a significantly larger user base.
In the second quarter, Claude had 56 million monthly active users globally, a fraction of ChatGPT’s user base. However, Claude’s year-over-year growth of approximately 640% far outpaced ChatGPT’s growth of 62%.
Both companies are vying to solidify their market positions. Anthropic has reportedly filed for a US initial public offering confidentially, while Reuters has indicated that OpenAI is also preparing to file for an IPO in the coming weeks.
