OpenAI’s push into advertising now appears to extend beyond what happens inside ChatGPT. An independent researcher found that a cookie associated with ChatGPT can reappear when the same browser visits websites that use OpenAI’s advertising pixel. It is most likely designed to give OpenAI a way to link ad interactions to activity that occurs later on participating sites.
The system centers on a cookie called __obi, according to a researcher who goes by the name Buchodi. The researcher found that ChatGPT can place the cookie in a browser, where it can persist for up to a year. When that browser later visits a site running OpenAI’s advertising technology, requests sent back to OpenAI can include the same identifier along with page and conversion data.
That does not mean OpenAI is attaching every off-site action to a named ChatGPT account. Buchodi did not observe the final server-side step that would join activity from an advertiser’s site to a specific user account. What the research did show is that the same OpenAI identifier can travel from ChatGPT to participating advertiser sites and back to OpenAI.
This isn’t new technology. It’s essentially a traditional third-party cookie in a new context. For marketers, it could mean better conversion measurement in a channel with few ad performance metrics.
However, consumers may object to these cookies more. That’s because ChatGPT users share far more personal information than they typically give a search engine or social platform. As a result, a system that links chatbot activity to off-platform behavior raises questions about consent, disclosure, and the extent of data advertisers should expect an AI platform to connect.
The consent language deserves scrutiny
There is also a question about how OpenAI classifies the cookie.
OpenAI lists __obi as an analytics cookie. Buchodi found that the cookie could reportedly be set when analytics consent was allowed, even if a user had declined marketing cookies.
That distinction matters because users may reasonably understand “analytics” to mean product or site measurement rather than cross-site advertising attribution. OpenAI has not publicly answered questions about why the cookie carries that label or whether analytics-only consent was intended to cover the reported behavior at the time the research was published.
For marketers using ChatGPT ads, that puts consent design and vendor due diligence on the list of things to understand before celebrating improved attribution. Knowing that a platform can measure more is different from knowing customers understand and accept how that measurement works.
It also means ChatGPT must comply with the many different laws governing the handling of personal information. That’s likely not the type of government oversight OpenAI has been asking for.
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Constantine von Hoffman is senior editor of MarTech. A veteran journalist, Con has covered business, finance, marketing and tech for CBSNews.com, Brandweek, CMO, and Inc. He has been city editor of the Boston Herald, news producer at NPR, and has written for Harvard Business Review, Boston Magazine, Sierra, and many other publications. He has also been a professional stand-up comedian, given talks at anime and gaming conventions on everything from My Neighbor Totoro to the history of dice and boardgames, and is author of the magical realist novel John Henry the Revelator. He lives in Boston with his wife, Jennifer, and either too many or too few dogs.
