A researcher says ChatGPT's ad cookie follows users onto advertiser sites
A technical investigation links OpenAI's `__obi` cookie to an advertiser pixel observed across more than a thousand hostnames.
What is being claimed
An independent investigation says OpenAI’s advertiser code sends a cookie named __obi, scoped to .openai.com, alongside information about pages visited on participating advertiser sites. The author says the mechanism was reproduced with two capture methods and observed across 936 advertiser pixels on 1,029 hostnames.
The report also says OpenAI support acknowledged the cookie after the author asked how it was categorized for consent purposes.
Why it matters
ChatGPT is an authenticated assistant that may contain sensitive conversation history. Any connection between an account-scoped identifier and activity on third-party sites deserves a much clearer explanation than ordinary ad-tech language.
What is not yet proven
The observed request path does not by itself establish every way OpenAI stores, links or uses the data. The report needs independent reproduction, and OpenAI has not yet supplied the detailed public response needed to close those questions.
What to watch next
The key issues are account linkage, consent categories, retention, advertiser access and whether refusing marketing cookies prevents the transfer. Until those are answered, the story remains developing.