OpenAI's __obi cookie tracks users after they leave ChatGPT

An independent researcher found that OpenAI sets a cookie called __obi in browsers using ChatGPT, which is then passed to advertising partners. The cookie lasts a year and uses SameSite=None, allowing cross-site tracking. OpenAI has not answered questions about its behavior.

• The __obi cookie lasts one year and uses SameSite=None
• Analysis covered 936 OpenAI pixels across 1,029 hostnames
• 736 of 932 decoded tokens were tied to logged-in users
• One identifier appeared across 10 different advertisers