OpenAI’s ChatGPT has surpassed 400 million weekly active users, a milestone that underscores the company’s growing reach across both consumer and enterprise markets, according to an X post from chief operating officer Brad Lightcap on Thursday.

The rapid expansion comes as OpenAI faces intensifying competition from rivals such as Elon Musk’s xAI and China’s DeepSeek, both of which have recently launched high-performing models aimed at disrupting OpenAI’s dominance. Despite this, OpenAI has seen significant traction in the business sector, with more than two million enterprise users now using ChatGPT at work — doubling from September 2024.

“ChatGPT recently crossed 400M WAU, we feel very fortunate to serve 5% of the world every week,” Lightcap wrote. He also noted that usage of OpenAI’s reasoning model API has surged fivefold since the launch of its o3 Mini model, which is designed to enhance logical inference and structured problem-solving capabilities.

chatgpt recently crossed 400M WAU, we feel very fortunate to serve 5% of the world every week

2M+ business users now use chatgpt at work, and reasoning model API use is up 5x since o3 mini launch

we’ll bring GPT-4.5 and GPT-5 to chat and the API soon, with unlimited GPT-5 for… https://t.co/7hfyUcIyBW

— Brad Lightcap (@bradlightcap) February 20, 2025

AI is reshaping the workplace: 2 million businesses now rely on ChatGPT

The surge in enterprise adoption represents a crucial validation of OpenAI’s strategy to position ChatGPT as not just a chatbot for casual queries, but as a serious productivity tool for businesses. Companies such as Morgan Stanley, Uber and T-Mobile have integrated OpenAI’s models into their workflows, using AI to generate reports, automate customer service and streamline decision-making.

Notably, OpenAI’s progress comes amid heightened scrutiny over the role of generative AI in business-critical applications. The company recently secured its first federal agency customer, USAID, which is deploying ChatGPT Enterprise to reduce administrative burdens and streamline partnerships, according to FedScoop. The expansion into government contracts suggests OpenAI is succeeding in navigating the regulatory hurdles that have slowed adoption of AI in public-sector institutions.

At the same time, OpenAI is deepening its presence in Japan through a joint venture with SoftBank, dubbed SB OpenAI Japan. The partnership, which involves a $3 billion annual investment from SoftBank, aims to integrate OpenAI’s technology into major Japanese enterprises, with initial deployments inside SoftBank’s own ecosystem, including its semiconductor subsidiary Arm and digital payments platform PayPay.

GPT-5 is coming: OpenAI’s next leap in artificial intelligence

Lightcap also revealed that OpenAI is preparing to launch GPT-4.5 and GPT-5, with the latter set to merge the company’s GPT and o-series models into a single, more powerful system.

“We’ll bring GPT-4.5 and GPT-5 to chat and the API soon, with unlimited GPT-5 for free users (plus users can run at even higher intelligence),” he wrote.

This move signals OpenAI’s ambition to consolidate its AI offerings into a unified model that can handle both general conversational AI tasks and more specialized reasoning-based applications.

By integrating the capabilities of its flagship GPT models with the structured problem-solving of the o-series, OpenAI is betting that a one-model-to-rule-them-all approach will give it a competitive edge over rivals that are still segmenting their AI offerings.

OPENAI ROADMAP UPDATE FOR GPT-4.5 and GPT-5:

We want to do a better job of sharing our intended roadmap, and a much better job simplifying our product offerings.

We want AI to “just work” for you; we realize how complicated our model and product offerings have gotten.

We hate…

— Sam Altman (@sama) February 12, 2025

The timing of the GPT-5 release is particularly critical. Musk’s xAI recently introduced Grok 3, a model that the company claims outperforms OpenAI’s GPT-4o in certain benchmarks, including math, science and coding. Meanwhile, DeepSeek’s rapid rise in China has added to the pressure on OpenAI to maintain its lead in AI sophistication and accessibility.

The AI wars: OpenAI, xAI and DeepSeek battle for global dominance

OpenAI’s expansion comes at a moment of fierce competition in the AI sector, with rival companies racing to secure market share in both consumer and enterprise applications.

Musk, who co-founded OpenAI before departing in 2018, has been vocal about his concerns regarding the company’s shift toward a for-profit model. The billionaire recently launched an unsolicited $97 billion bid to take control of OpenAI, a move that was swiftly rejected by the company’s board. OpenAI has since positioned itself as the leader in enterprise AI deployments, with Microsoft’s backing providing both financial stability and cloud infrastructure.

Meanwhile, DeepSeek has disrupted the market with low-cost, open-source AI models that have gained traction, particularly among developers wary of OpenAI’s pricing model. The Chinese firm has claimed that it trained its latest model for under $6 million — an order of magnitude lower than what OpenAI and xAI are spending on comparable systems.

What’s next for OpenAI? The future of AI in business and beyond

OpenAI’s latest user metrics suggest that the company is still expanding at a rapid clip despite the mounting competition. The leap from 300 million to 400 million weekly active users in just three months indicates that demand for AI-powered tools continues to grow, with businesses increasingly integrating them into their everyday operations.

The launch of GPT-5 will be a crucial test of OpenAI’s ability to maintain its leadership in AI. If the model delivers on promises of higher reasoning capability, better personalization and improved efficiency, it could cement OpenAI’s position as the go-to provider for both consumer and enterprise AI applications.

However, with Musk’s xAI, DeepSeek and Google’s Gemini models all vying for dominance, OpenAI cannot afford to slow down. The next 12 months will likely determine whether it remains the uncontested leader in generative AI, or whether a new player will disrupt the balance of power in artificial intelligence.