According to analytics firm Sensor Tower's State of AI Report 2026, ChatGPT's market share fell to 46.4% by the end of May, down from more than 50% in January.

The decline comes as users increasingly turn to alternative AI assistants, with Gemini capturing 27.7% of the market and Claude reaching 10.3%. Other platforms, including Grok, Perplexity, DeepSeek and Meta AI, each account for less than 5%.

Despite the drop in market share, ChatGPT remains the world's most widely used AI assistant, boasting more than 1.1 billion monthly users. Sensor Tower also noted that the chatbot became the fastest application ever to surpass one billion monthly users, cementing its position as the industry's leading platform.

The report found that users are becoming more willing to switch between AI assistants based on performance, ecosystem integration and company decisions.

It noted that OpenAI's agreement with the U.S. Department of Defense in February coincided with a measurable increase in app uninstalls, suggesting that "brand trust and values alignment matter to users, not just features."

Meanwhile, Gemini has gained momentum through its integration across Google's ecosystem, while Claude has built a strong reputation for productivity and is closing in on ChatGPT's user-retention rate.

The broader AI market continues to expand rapidly. Sensor Tower estimates that users are on track to download nearly 2.3 billion AI apps and spend more than $4.2 billion during the first half of 2026, up from $1.83 billion during the same period last year. The report said the figures indicate the industry is gradually shifting its focus from rapid user growth toward monetization.

OpenAI has also expanded advertising within ChatGPT, with about 17% of daily users seeing ads by May. At the same time, ChatGPT is increasingly directing shopping traffic to retailers including Walmart, Target and Costco, highlighting the growing influence of AI assistants on consumer purchasing decisions.