OpenAI Confidentially Files for IPO — Largest AI Startup Heads for Public Markets
OpenAI filed its confidential S-1 with the SEC on or around May 21, with a public offering possible within weeks. The filing, first reported by CNBC and corroborated by the Wall Street Journal, triggers a mandatory quiet period before OpenAI can solicit investor interest publicly.
The company enters the IPO process at a scale no private AI lab has reached before: $122 billion raised to date, $852 billion valuation from its last round, and a run-rate that analysts estimate north of $10 billion annually. GPT-5.5, Codex, ChatGPT Finance, and the 900 million weekly active users on the platform are the commercial pillars behind those numbers.
The Race Against Anthropic
Prior to this week, prediction markets gave Anthropic and OpenAI roughly equal odds of being the first AI frontier lab to go public. That calculus shifted immediately. Traders on major prediction platforms now assign OpenAI a commanding lead.
For OpenAI, the strategic argument for moving first is direct. “Getting to public markets first is very important,” one source close to the process told CNBC. A successful IPO would lock in OpenAI’s capital position, establish a public valuation anchor, and give the company a liquid currency for acquisitions and employee retention that Anthropic cannot currently match.
Structural Complexity
OpenAI’s path to public markets is not straightforward. The company spent most of 2025 restructuring from its non-profit/capped-profit hybrid into a conventional for-profit entity — a legal transition that is still completing. How the non-profit retains governance rights, and what percentage of equity flows to the public, will be among the most-watched elements of the final S-1.
Microsoft holds a significant equity stake, estimated in the tens of billions of dollars at current valuations. How that stake is treated — and whether Microsoft retains any structural advantage on model access post-IPO — is the question that enterprise AI buyers will scrutinize most.
Six state attorneys general have already asked the SEC to investigate Sam Altman’s personal investments ahead of any IPO, citing potential conflicts with the company’s non-profit restructuring. That probe was filed months ago; it does not appear to have slowed the filing timeline.
What the S-1 Will Show
The filing will be the first public look at OpenAI’s actual cost structure. The company is known to burn heavily on compute: internal estimates cited by analysts peg training and inference costs at over $5 billion annually at current scale, with Codex’s agentic workloads adding meaningfully to the inference line.
Revenue diversification will also come under scrutiny. ChatGPT subscription revenue, API revenue, enterprise contracts, and the emerging Codex Pro subscription tier will each need to be broken out. OpenAI’s arrangement with Microsoft — which includes a significant revenue-sharing clause — will draw particular attention from institutional investors evaluating how much of the top line OpenAI actually owns.
The IPO would be the largest US tech debut since Cerebras raised $5.55 billion at $185 per share in a Nasdaq listing earlier this year.