ChatGPT's share of AI assistant use slips below 50% for the first time

Sensor Tower's State of AI 2026 report, summarized in TechCrunch, puts ChatGPT below 50% of AI assistant use for the first time, with its share at 46.4% in May, down from over 50% in January. Gemini sits at 27.7%, Claude at 10.3%, and everyone else (Grok, Perplexity, DeepSeek, Meta AI) is under 5%. On monthly active users the gap is still wide: 1.1 billion for ChatGPT, 662 million for Gemini, 245 million for Claude. Spending in the first half of 2026 reaches $4.2 billion against $1.83 billion in the same period of 2025, more than double year over year.

A few details under the headline matter more than the share number. Claude's subscription conversion rate is 13%, which Sensor Tower calls industry-leading and which fits Anthropic's bet on paying developers over free traffic. By May, 17% of daily ChatGPT users were seeing ads, the visible side of OpenAI's pivot from pure growth to monetization. Users now switch platforms based on values alignment and use case, the report finds, a different posture from the early grab for whatever was first.

ChatGPT is still the default. But "default" with a 46% share, against competitors selling on price, openness, or work integration, is a very different market than dominance, and the second half of 2026 is where pricing and feature pressure will compound.

Why it matters

If you sell into consumer or prosumer AI use, plan for a real second and third option, not a single API to court. If you build on top of an assistant, the share shift is also a signal about which assistant your end users may already be carrying daily.