Claude’s monthly active users surged 1,260 percent year over year in the third quarter of 2026, the fastest growth among the seven AI assistants tracked by Sensor Tower, though it still represented only about 4 percent of their combined users.

The growth took off in the United States in March, following OpenAI’s partnership with the U.S. Department of War and a Super Bowl ad campaign; Claude downloads rose 765 percent year over year in the first quarter, 1,264 percent in the second and 891 percent in the third.

Even as Claude gained ground, ChatGPT remained the largest assistant, with 1.4 billion monthly active users—more than 60 percent of the group—while Gemini ranked second with 591 million, or about 26 percent.

Meta AI grew 675 percent year over year, Gemini 166 percent and ChatGPT 70 percent, while Perplexity declined 5 percent; ChatGPT is responding to competition by combining Chat and Work, a move Claude had already made.

People are using AI assistants more intensively: since the start of 2026, sessions per user rose 44 percent and time spent increased 50 percent across the group, while Claude users averaged 23 sessions and 39 minutes a week.

ChatGPT users averaged 32 sessions per week, but their time spent per user fell 5 percent.

Claude’s audience is primarily web-based: from April to October, 73 percent of its users accessed it only on the web and 17 percent only through the app, unlike ChatGPT, whose users were more likely to rely on the app.

Paid ads accounted for about 22 percent of downloads across the group in 2026, up five percentage points from a year earlier, with the share reaching 62 percent for Muse and 52 percent for Meta AI.

U.S. advertising spending by the assistants rose 429 percent year over year in the third quarter, with ChatGPT taking 54 percent of group spending so far in 2026 and Claude 15 percent; Meta’s Muse and xAI’s Grok Bot were also capturing substantial shares in the fourth quarter.

The figures are drawing investor attention as Anthropic prepares for an I.P.O. and a reported valuation of about $1.5 trillion; its annualized revenue recently reached $68 billion, and Sensor Tower says its app and web activity estimates correlate with quarterly revenue at 0.85.

The estimates need context: Claude’s rapid percentage gains come from a small base, group downloads fell 11 percent in the third quarter, and Claude users’ 39 weekly minutes were below the 43-minute group average.

App statistics also capture only part of Anthropic’s business, which includes developer and API revenue and tools such as Claude Code.