OpenAI ushered in the current AI era with the release of ChatGPT, but a lot of competitors have emerged since that day in November 2022.
Now, ChatGPT’s share of the global AI assistant market has fallen to below 50% for the first time. According to the newly released “State of AI 2026” report from data analytics firm Sensor Tower, ChatGPT’s fall came in March, hitting just 46% by May.
Sensor Tower measures market share through a “true audience” metric, which looks at usage across desktop, mobile apps, and the mobile web.
The news comes just over a week after OpenAI announced it has taken the first step toward pursuing an IPO. The company has yet to disclose a stock listing date.
In contrast to ChatGPT, Sensor Tower reports that Google’s Gemini and Anthropic’s Claude had 28% and 10% of the market share, respectively.
The “global” data evaluates 25 markets, with some looking even more favorable for ChatGPT’s competitors. Take the United States, where Claude’s market share rose from just 5% in December 2025 to 14% in May.
User concerns over DoD deal may have played a role
Sensor Tower attributes this shift, in part, to OpenAI’s deal with the U.S. Department of Defense.
Anthropic initially held an agreement but refused to allow Claude to be used for things like mass surveillance and autonomous lethality. OpenAI claimed its late February deal had the same “red lines,” but it’s also allowing the Pentagon to use ChatGPT for “all lawful purposes.”
Some ChatGPT users jumped ship for Claude in response to the news, Sensor Tower reports.
Fast Company has reached out to OpenAI for comment. We will update this post if we hear back.
A lightning-fast road to 1 billion
Despite the decline in market share, ChatGPT in May became the fastest mobile app to reach one billion users.
Across all platforms, ChatGPT had 1.11 billion users worldwide, still a substantial lead over Gemini’s 662 million users and Claude’s 245 million users.
There appears to be plenty of AI use to go around. Sensor Tower projects global users will spend 36 billion hours on generative AI apps over the first half of 2026. That figure is more than double the 17.2 billion hours spent from January to June 2025.
