ChatGPT's market share fell below 50% for the first time as users shift to Google's Gemini and Anthropic's Claude, reshaping the AI assistant landscape.

What happened: ChatGPT's share dropped to 46.4% by end of May 2026, down from over 50% in January, while Gemini rose to 27.7% and Claude to 10.3%. OpenAI's DoD partnership in February triggered a measurable spike in uninstalls, and users are increasingly willing to switch between assistants based on brand values and specific use cases.

Why it matters: Despite still leading with over 1.1 billion monthly users, ChatGPT's dominance is eroding fast enough that investors and the industry are reassessing which AI assistants will capture long-term revenue. Anthropic's Claude stands out with a 13% subscription conversion rate—highest in the field—suggesting users are willing to pay for productivity features, not just novelty.

What to watch: ChatGPT began serving ads in February and by May was reaching an average of 17% of daily users with advertisements; this monetization strategy beyond subscriptions will determine whether OpenAI can defend its market position. Also watch Anthropic's subscription conversion metric and regional spending patterns—Asia leads downloads but lags North America and Europe in in-app spending.