OpenAI's Codex passes 2 million weekly active users
Usage roughly quintupled since the start of 2026, from about 1 million monthly developers in February to over 2 million weekly users by mid-March, OpenAI figures showed.
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OpenAI’s Codex, its coding agent built on the GPT-5 family, passed 2 million weekly active users, according to figures OpenAI disclosed during a period of fast growth for the product. More than 1 million developers had used the tool in the month before its desktop app launched in February 2026; usage reached 1.6 million weekly active users soon after the GPT-5.3-Codex release that month, before surpassing 2 million weekly by mid-March — roughly a fivefold increase since the start of the year.
Companies including Cisco, Nvidia, Ramp, Rakuten and Harvey were reported to be deploying Codex across their developer teams during this period. The milestone placed Codex alongside rival coding agents from Anthropic, Google and a wave of startups in a market where agentic coding tools had become one of the clearest cases of measurable enterprise AI adoption, in contrast to the more contested claims made for general-purpose chat assistants. As with most user-count disclosures from AI labs, the figures came from OpenAI itself rather than independently audited usage data.