OpenAI added Codex to the ChatGPT mobile app today, making the tool available on iPhone and Android for all users, including those on free plans. What Codex actually does is worth understanding, because the name sounds technical but the idea is simple: you give it a job, it works on that job on your computer or company server while you do other things, and you check back in when it needs you.
The mobile version is not a standalone app. It connects to wherever Codex is already running, your laptop, a Mac Mini on your desk, or a server your company manages, and shows you live updates. You can approve what it does next, change direction, or start something new, all from your phone. Your files and company data stay on the original machine and are not rerouted through your phone.
The growth behind this product is the part that deserves attention. Codex went from 600,000 weekly users in January to 4 million by late April. That is a seven-fold increase in roughly four months. Inside companies with enterprise ChatGPT accounts, usage of Codex grew six times over since January alone. Those are not casual adoption numbers.
The reason for that growth is competitive pressure. Anthropic, the company behind the Claude AI, has been winning enterprise deals at a pace that caught OpenAI off guard. Its Claude Code product gained serious traction with developers and business teams through last year, and Anthropic's overall revenues climbed to a reported $19 billion annualised run rate by early March. OpenAI's own internal assessment, as reported by The Wall Street Journal, was that the company had spread itself too thin across too many products.
The response was a strategic pivot. OpenAI announced in March that it would merge ChatGPT, Codex, and its Atlas browser into a single desktop platform. Codex would be the foundation. The idea is to build one tool that can write code, browse the web for context, analyse data, and manage long-running tasks, all without the user needing to switch between applications. Today's mobile update is part of that build-out, extending the same platform to your phone.
There is a detail here that goes beyond developers. Inside OpenAI itself, more than 80 percent of the company uses Codex, and not just engineers. Teams use it to write weekly briefings, review contracts, synthesise research, and draft requirements. Separately, coding-related activity among enterprise ChatGPT users outside of engineering and IT departments rose 36 percent in the past six months. The tool is quietly moving from a developer product into a general workplace tool.
For companies evaluating AI tools right now, the practical question is not which AI writes better code. The competition between OpenAI and Anthropic has evolved into a race to build the platform that runs the most workflows in your organisation. OpenAI is betting that Codex, attached to the massive ChatGPT user base, becomes the default environment for that. Anthropic is betting that its reputation for reliability and careful behaviour in enterprise settings wins those contracts before the platform race is decided.
The mobile update also adds HIPAA compliance for Codex in healthcare enterprise accounts, the ability to connect to remote company servers securely, and expanded team-management controls. None of those features make headlines, but they are exactly the kind of details that procurement and IT teams look at when deciding whether to sign a multi-year contract.