ChatGPT has crossed a major usage threshold, with Similarweb data indicating that monthly active users of its iPhone and Android applications worldwide have risen above 1 billion. The trajectory underscores how quickly generative AI has moved from an emerging technology into a mainstream digital service, while OpenAI is increasingly relying on enterprise adoption to convert that enormous user base into a broader commercial platform.

ChatGPT’s Mobile Audience Has Expanded More Than 25-Fold

The attached Similarweb chart shows ChatGPT’s estimated monthly active mobile users increasing from roughly 40 million in early 2023 to more than 1 billion by September 2026. That represents an increase of more than 25 times in approximately three years, although the data should be understood as an estimate of app activity rather than a direct count of unique individuals. Similarweb defines a monthly active user based on device activity and does not distinguish users from devices.

The acceleration was particularly pronounced during 2025, when the chart shows monthly active users moving from approximately 500 million to more than 750 million within several months. Growth subsequently continued at a slower but still substantial pace, reaching the billion-user threshold in 2026. The scale places ChatGPT among the largest consumer internet applications and gives OpenAI an unusually broad distribution channel for new AI capabilities.

Enterprise Adoption Is Becoming a Second Growth Engine

Consumer reach is only one component of OpenAI’s commercial strategy. CFO Sarah Friar said at a Goldman Sachs conference that OpenAI’s enterprise division grew 32% month over month in July, while the company’s overall revenue run rate increased 20% from June to July. Friar described the enterprise business as having been “on a tear,” indicating that corporate demand is becoming an increasingly important source of growth.

OpenAI has previously said that enterprise revenue accounted for more than 40% of its revenue and was on track to reach parity with consumer revenue by the end of 2026. The company is also expanding its enterprise footprint through APIs, coding tools, AI agents and partnerships designed to embed its models into corporate workflows.

This shift matters because enterprise customers can generate substantially different economics from consumer users. Corporate contracts can involve recurring subscriptions, API consumption and large-scale deployment across employees, potentially making enterprise adoption a more predictable monetization channel as AI usage becomes embedded in business operations.

Scale Is Increasing the Importance of Monetization

The rapid growth in users is occurring alongside an expansion of OpenAI’s revenue model. Beyond ChatGPT subscriptions and enterprise contracts, the company has begun building an advertising business, which OpenAI has reportedly brought to an annualized revenue run rate of approximately $1 billion. The diversification reflects the economic challenge created by operating advanced AI models: enormous usage can translate into substantial computing and infrastructure costs, making monetization efficiency increasingly important.

OpenAI is simultaneously increasing the capabilities of its models. The September launch of GPT-6 Astra is designed to expand performance in computer use, browsing, software engineering, cybersecurity and professional work, potentially increasing the range of enterprise tasks that can be automated or augmented. OpenAI says its broad consumer and enterprise distribution provides a direct route to customers for these capabilities.

The Next Test Is Turning Usage Into Sustainable Economics

For investors and the broader technology industry, the significance of the 1 billion-user milestone extends beyond headline scale. The more important question is whether OpenAI can maintain user engagement while converting that reach into recurring, high-margin revenue without allowing inference and infrastructure costs to rise at a similar pace.

Going forward, the key indicators will include enterprise revenue growth, paid conversion, advertising revenue, API consumption, user retention and the cost of serving increasingly capable models. ChatGPT’s mobile expansion demonstrates extraordinary consumer adoption, while the accelerating enterprise business suggests that OpenAI is building a second commercial pillar. The strategic challenge now is to transform that unprecedented reach into a durable business model capable of supporting the enormous capital requirements of frontier AI.