More than three years after the launch of ChatGPT, the artificial intelligence assistant market is becoming increasingly competitive, with OpenAI’s dominance slipping below the 50 per cent threshold for the first time as rivals gain traction.

According to Sensor Tower’s State of AI Report 2026, ChatGPT remains the world’s most widely used AI assistant, boasting more than 1.1 billion monthly users.

However, its market share declined to 46.4 per cent by the end of May from over 50 per cent in January, as competitors such as Gemini and Claude expanded their user bases.

Google’s Gemini has emerged as the closest challenger, with 662 million monthly users and a 27.7 per cent market share, while Anthropic’s Claude has grown to 245 million users, accounting for 10.3 per cent of the market. Other platforms, including Grok, Perplexity, DeepSeek and Meta AI, each hold less than five per cent market share.

The report highlighted growing consumer willingness to switch between AI assistants, suggesting that competition is increasingly driven by trust, ecosystem integration and specialised capabilities rather than user familiarity alone.

Sensor Tower noted that OpenAI’s partnership with the United States Department of Defense in February coincided with a measurable increase in app uninstalls, indicating that corporate decisions and brand perception can influence user retention.

Meanwhile, Gemini has benefited significantly from its integration across Google’s ecosystem, while Claude has strengthened its position through productivity-focused features and improved user retention.

Despite rising competition, ChatGPT continues to record strong growth. Sensor Tower recently reported that it became the fastest application ever to reach one billion monthly users. OpenAI, which reports weekly active users rather than monthly figures, last disclosed 900 million weekly active users in February.

The broader AI app industry is also witnessing rapid commercial growth. Sensor Tower estimates that global AI app downloads will approach 2.3 billion in the first half of 2026, while consumer spending on AI applications is expected to exceed $4.2bn during the period.

The projected spending represents a sharp increase from the $1.83bn recorded in the first half of 2025, underscoring the industry’s shift from prioritising user acquisition to monetisation.

However, the report noted that growth rates for both downloads and spending are beginning to slow, suggesting the AI market may be entering a more mature phase even as overall usage continues to rise.