ChatGPT share falls below 50% as Gemini and Claude gain users

Sensor Tower measured OpenAI's ChatGPT at 46.4% of AI assistant market share at the end of May, the first time the chatbot fell below 50%.

OpenAI runs the largest assistant by user count. The analytics firm Sensor Tower put ChatGPT at more than 1.1 billion users per month, ahead of Google Gemini at 662 million and Anthropic's Claude at 245 million. OpenAI last gave a public usage figure in February, when the company said ChatGPT had 900 million users per week.

OpenAI has less leverage than a category leader with more than 1 billion users might expect, because rivals have claimed clear lanes. Gemini reached 27.7% share by May's end, and Claude reached 10.3%. xAI's Grok and smaller rivals each held less than 5%.

Users also switch between assistants with less friction than the first wave of consumer AI suggested. Sensor Tower said users uninstalled ChatGPT at a higher rate after OpenAI struck a February deal with the U.S. Defense Department. That pattern gives brand trust a place beside model quality, price and workflow fit.

Google has a distribution edge through Android, Search and Workspace. Anthropic has built Claude around work tasks, long documents and coding. OpenAI has the broadest consumer base, but user behavior now looks more like the browser market or cloud software market: customers keep several tools close and choose one for the job in front of them.

Market context

Sensor Tower expects users to download about 2.3 billion AI apps and spend more than $4.2 billion on them in the first half of 2026. The firm counted $1.83 billion in spending in the first half of 2025.

Executives at AI companies can read those figures as a clear signal. Consumer AI has moved from land grab to revenue test. Product teams still need growth, but investors will press harder on paid conversion, retention and advertising yield.

Sensor Tower also recorded slower growth in downloads and spending. Users in Asia downloaded 3.3% fewer AI apps in the first quarter of 2026, with users in China and India accounting for much of the drop. Consumers in Asia download the most AI apps, while consumers in North America and Europe spend more inside those apps. AI companies will use that split to decide where to launch premium tools, local pricing and bundled subscriptions.

Claude gives Anthropic the cleanest monetization signal in the report. Sensor Tower said 13% of Anthropic users pay for a subscription, the highest conversion rate in the field. Investors will watch that figure because paid AI use tends to reveal work value faster than download charts do.

Time spent also favors the largest assistants. Sensor Tower expects users to spend about 36 billion hours in AI apps in the first half of 2026, up from 17.2 billion hours in the first half of 2025. The top three assistants account for 89% of time spent in AI assistant apps, which gives OpenAI, Google and Anthropic a strong base for subscriptions, ads and commerce.

Ads and shopping

OpenAI began testing ads in ChatGPT in February. By May, the company showed ads to an average 17% of users each day, according to Sensor Tower. Software and shopping advertisers bought the most inventory, with media and entertainment brands close behind.

Ads give OpenAI a second revenue line beyond subscriptions. They also create a product risk. Users adopted ChatGPT as a clean answer engine and work tool, so OpenAI has to place commercial results without damaging trust in the response. Google has spent decades managing that trade-off in Search. OpenAI now faces a version of the same problem inside a chat interface.

Shopping may carry more value than display ads. OpenAI has turned ChatGPT into a retail referral channel as the company adds product discovery and checkout integrations. Sensor Tower said ChatGPT sends referral traffic to Target, Walmart and Costco. Amazon blocked ChatGPT's web crawlers, and Sensor Tower saw flat referral traffic from ChatGPT to Amazon.

Retailers have started to answer with their own assistants. Walmart has embedded AI search and product help into its shopping flow. Amazon has pushed Rufus inside its app. Sensor Tower found that Amazon shoppers who used Rufus spent more time in the app and converted at higher rates than shoppers who skipped it.

That finding gives retailers a reason to fund AI inside their own apps instead of sending the full customer journey to a third-party assistant. If shoppers ask ChatGPT for product help, retailers want the referral. If shoppers open a store app, retailers want their own assistant to close the sale.

Strategic read

OpenAI faces two linked tasks: defend usage share and build revenue from a massive consumer base. The company can use subscriptions, ads and shopping, but each path adds pressure on user trust.

Google can push Gemini through products that users already open each day. Anthropic can sell Claude to workers who care about output quality and document-heavy tasks. xAI can use Grok's tie to X and its own model releases to stay visible, even from a smaller base.

The assistant market now rewards execution across distribution, retention and paid conversion. Model quality still matters, but users have shown they will move when another assistant fits a task, a workflow or a set of values better.

OpenAI set the consumer benchmark with ChatGPT. Sensor Tower's 2026 data shows a market where OpenAI leads, Google scales through ecosystem reach and Anthropic converts a smaller base into paid users at a higher rate. Buyers and users will decide the next phase by paying for assistants that save time, fit their tools and keep their trust.