The one that matters
A researcher caught OpenAI's ad pixel tying ChatGPT accounts to browsing everywhere else
OpenAI's collector at bzr.openai.com sets an account-tied __obi cookie, and every site buying ChatGPT ads embeds an OpenAI pixel that sends that cookie back with page data: products searched, articles read, purchases. The author reproduced the mechanism on their own phone with two independent capture methods, across months of traffic covering 936 advertiser pixels on 1,029 hostnames.
Why it matters
The quiet part of ChatGPT's ads launch is now measured, not suspected: Meta-style cross-site tracking from the company holding your most private questions. If you ship on OpenAI, run ads there, or advise anyone who does, cookie consent and pixel policy just became a real compliance surface.
