OpenAI and Anthropic have both confidentially filed draft S-1 registration statements with the SEC within days of each other, setting the stage for a historic dual listing that pits the two most prominent AI companies directly against each other in the public markets.

Key Highlights

  • Both filed confidentially: Anthropic filed first, followed one week later by OpenAI, which confirmed its confidential S-1 submission to the SEC while stating it has "not decided on timing yet" for any public debut.
  • Valuation gap: Anthropic was most recently valued at $965 billion following a $65 billion Series H funding round in May 2026, surpassing OpenAI's $852 billion valuation from March, making Anthropic the world's most valuable startup.
  • OpenAI eyes September: OpenAI has told investors it is targeting a public listing as early as September 2026, though it framed the filing as preserving flexibility rather than committing to a specific timeline.
  • Prediction markets favour Anthropic first: Implied probability on prediction markets stands at approximately 82.5% in favour of Anthropic completing its IPO before OpenAI.

OpenAI and Anthropic, the two leading generative AI companies, have both taken the first formal steps toward public listings, filing confidential draft S-1 registration statements with the U.S. Securities and Exchange Commission within a single week of each other in early June 2026.

Anthropic moved first, filing its confidential S-1 and disclosing the move publicly. One week later, OpenAI announced it had submitted its own draft registration statement, stating that it expected the document to surface regardless and chose to get ahead of the news. OpenAI said it had "not decided on timing yet" for any potential offering, describing the filing as preserving flexibility, while separately telling investors it was targeting a listing as early as September 2026.

Anthropic surpassed OpenAI in private market valuation for the first time in May 2026, following a $65 billion Series H round that valued it at $965 billion. OpenAI was most recently valued at $852 billion in March 2026, putting it behind Anthropic heading into the listing process.

Both companies have been spending heavily on data centre capacity, chip procurement, and AI infrastructure, and the move to public markets reflects the limits of private fundraising at their scale. OpenAI completed a $122 billion private round earlier in 2026, while Anthropic's $65 billion round was led by Altimeter Capital, Dragoneer, Greenoaks, and Sequoia Capital.

The dual listing race carries strategic significance beyond capital raising. Those advising both companies have indicated that whichever firm lists first will benefit from deeper pools of investor cash before lock-up periods expire and simultaneous insider selling becomes a factor.

Both companies are loss-making. Going public will require financial disclosures that have so far remained private. If Anthropic achieves a $1 trillion valuation at listing, it would rank among the largest IPOs in history.