For the first time since ChatGPT launched in November 2022, its weekly active users in the United States declined month over month. Not plateaued. Declined. While that was happening, downloads of Anthropic's Claude tripled to 21 million in a single month.

The data comes from multiple sources. Apptopia tracked the ChatGPT decline. Sensor Tower tracked Claude's surge. And Ramp, which processes $100 billion in annual card and invoice spending from 50,000 businesses, showed that nearly a third of American companies now pay for Anthropic products, up more than 6 percentage points in a single month. OpenAI's business adoption held flat at 35%.

This is the tipping point everyone kept saying would never come.

The Numbers Tell a Story OpenAI Does Not Want to Hear

OpenAI still claims 900 million weekly active users globally. ChatGPT still leads with roughly 68% market share. But market share is a lagging indicator, and the leading indicators are all pointing the same direction: toward Anthropic.

Claude's App Store downloads briefly surpassed ChatGPT. ClaudeBot now crawls the web 62% more than GPTBot. Claude Sonnet is used by 42.8% of surveyed developers, making it the most widely adopted model in professional coding workflows. Claude Code has 1.6 million weekly active users and is growing fast.

Forbes reported a 1,487% surge in users switching from ChatGPT to Claude. That number sounds absurd until you look at the underlying data, and then it just sounds like momentum.

Why This Is Happening Now

Two forces are converging. First, OpenAI degraded its own product. The company has been aggressively cutting costs, and users noticed. Quality complaints have been all over social media for months. When your product gets visibly worse, your most demanding users leave first. Those users went to Claude.

Second, Anthropic nailed the developer market. Claude Code is not just a coding assistant. It is a full development environment that developers are building their workflows around. Once a developer builds their pipeline around Claude, switching costs become real. OpenAI's Codex has 3 million weekly users, up from 2 million. That is growth. But Claude is growing faster in the segment that matters most: the users who influence what tools everyone else uses.

OpenAI Knows

The company's response to the Financial Times was revealing. OpenAI said it "did not recognize" the data showing its decline, then immediately pivoted to bragging about Codex users and API token processing. That is not the response of a company that feels secure. That is the response of a company that knows the narrative is shifting and is scrambling to control it.

OpenAI also pointed to its ad pilot reaching $100 million run rate in six weeks. Read that again. The company that was supposed to build AGI is now bragging about ad revenue. That is not a sign of strength. That is a sign that the subscription business is not growing fast enough to sustain an $85 billion annual burn rate.

The Bottom Line

ChatGPT is not dying. It still has 900 million weekly users. But for the first time, the trajectory is no longer straight up. Anthropic is eating into OpenAI's lead from two directions at once: developers who care about quality and businesses who care about precision. Those are the exact users who drive platform adoption.

OpenAI is about to IPO. Anthropic is about to IPO. The market will decide which trajectory it believes. Right now, the data says Claude is gaining ground faster than anyone expected, and ChatGPT is losing it for the first time ever.

Data sourced from Financial Times, Ramp, Sensor Tower, Apptopia, Statcounter, Forbes, and Business Insider.