ChatGPT has crossed one billion monthly active users, according to Sensor Tower data released in early June. That makes it the fastest app to reach the milestone, getting there in about three years and outpacing Google Maps, TikTok, Instagram and YouTube.
The same dataset, however, shows why Anthropic has its own story. Claude has about 56 million monthly active users, far below ChatGPT’s one billion, but its year-over-year growth is about 640% versus ChatGPT’s 62%. In absolute scale, OpenAI is far ahead; in momentum, Claude is still climbing the steep part of the curve.
Sensor Tower also found that US ChatGPT users who installed Claude in the first quarter of 2026 spent 5% less time in ChatGPT one month later than their average over the previous eight months. That points to Claude taking attention from existing ChatGPT users, not only finding new ones. With Anthropic filing confidentially for a US listing on June 1 and OpenAI expected to follow within weeks, investors now have to weigh scale against growth.
Sources：Reuters and Yahoo Finance report on ChatGPT reaching one billion monthly users; Cryptopolitan coverage of Claude engagement gains; CocoLoop