ChatGPT has lost the market majority it held since November 2022, dropping to 46.4% of the global AI-assistant market by the end of May 2026. This marks the first time OpenAI's flagship chatbot has held less than half the market, according to Sensor Tower's State of AI 2026 report. The shift reflects a maturing market where newer competitors are growing faster than the pioneer, even as ChatGPT's absolute user base continues to expand.

The decline has been steady and measurable. In December 2024, ChatGPT commanded 65.3% of the market. By March 2026, it fell below 50% for the first time. Three independent tracking firms confirm the trend: Sensor Tower measured the drop through unique monthly users across mobile and web, Apptopia tracked app-specific share falling from 69.1% in January 2025 to 45.3% in early 2026, and Similarweb's web-traffic data showed ChatGPT's share declining from roughly 87% in early 2025 to 52.7% by May 2026.

Which AI Assistants Are Gaining the Most Ground?

Google Gemini and Anthropic's Claude are the primary beneficiaries of ChatGPT's erosion. Gemini climbed to 27.7% market share by May 2026, up from just 6% in early 2025, while Claude reached 10.3%. The growth patterns reveal different strategies: Gemini's expansion is almost entirely a distribution story, while Claude is building strength in enterprise spending.

Gemini's rise is powered by integration into Google's ecosystem. By folding Gemini into Search, Android, and Workspace rather than requiring users to download a separate app, Google reached 662 million monthly active users by May 2026. However, a wrinkle emerged in the second quarter of 2026: new app downloads for Gemini cooled to 22% from a peak of 34% in late 2025, suggesting growth now comes more from pre-installation and cross-promotion than from users actively seeking it out.

Claude's consumer numbers appear modest at 245 million monthly active users and 10.3% market share, but the company's real strength lies elsewhere. Claude converts free users to paid subscribers at 13.0%, the highest rate among major assistants tracked. More significantly, Anthropic has pulled ahead of OpenAI on the enterprise side, where companies pay for API access. Menlo Ventures, an Anthropic investor, found that Anthropic captured roughly a third of enterprise large language model spending in 2026, ahead of OpenAI's mid-20s percentage and Google's low-20s share.

How Is This Playing Out in Australia?

Australia's market reflects the global shift. Telsyte's June 2026 research counted more than 17 million Australians using AI tools monthly, with ChatGPT still leading at 13.8 million users. However, Gemini's local user base has grown to 9.1 million, roughly two-thirds the size of ChatGPT's, while Claude reached 2.9 million. Nearly four in five Australian AI adopters still use ChatGPT specifically, but that dominance is under real pressure for the first time since the category existed.

Broader adoption patterns show AI is becoming embedded in Australian work and business. Separate research from ROI.com.au found that 58% of Australians now use AI tools monthly overall, two in three Australian workers use AI on the job, and more than half do so without their employer's sign-off. Roughly 43% of Australian small and medium businesses report using AI in some form, a figure that continues climbing as procurement teams catch up to informal staff adoption.

Why OpenAI Still Leads on Revenue Despite Losing Market Share

Market share and revenue tell different stories. ChatGPT's weekly active users crossed 900 million on February 27, 2026, and monthly active users passed 1 billion in June 2026, making it the fastest app in history to reach that milestone. Annualized revenue crossed $25 billion by February 2026, up from roughly $20 billion in 2025 and $6 billion in 2024.

The apparent contradiction resolves when you examine the underlying dynamics. OpenAI is not shrinking; it is growing more slowly than its rivals. ChatGPT still adds tens of millions of users every quarter, but Gemini and Claude are adding them faster. This is the classic pattern of a maturing market: the pioneer keeps growing in absolute terms while newer entrants eat into its share of the total pie. Mobile app revenue alone hit $1.35 billion in 2025, up 673% year over year from $174 million in 2024, demonstrating that ChatGPT's business remains robust even as its market dominance erodes.

Key Factors Driving the Market Shift

• Distribution Strategy: Google's integration of Gemini into existing products like Search and Android gave it reach to hundreds of millions of users without requiring separate downloads or active user acquisition.
• Enterprise Focus: Anthropic's emphasis on coding tools and agentic workflows, where Claude models rank well on independent benchmarks, has made it the preferred choice for companies paying for API access.
• Market Expansion: The overall AI-assistant market is growing rapidly, meaning all three major players are adding users in absolute terms while their relative shares shift.
• Conversion Rates: Claude's 13% free-to-paid conversion rate, the highest among tracked assistants, shows that user quality and willingness to pay vary significantly across platforms.

The data from multiple independent trackers paints a consistent picture: ChatGPT's dominance is eroding, but the company remains the largest player by market share and revenue. The shift reflects not OpenAI's decline but rather the maturation of a market that was once a near-monopoly. As AI assistants become more commoditized and integrated into everyday tools, the competitive landscape will likely continue to fragment, with different players winning in different segments: consumer reach, enterprise adoption, and specialized use cases.