--- title: ChatGPT now knows what you do on other websites via ad... description: OpenAI's ad measurement system sets a cookie called __obi, scoped to .openai.com with SameSite=None, that gets sent back to OpenAI whenever a user visits any... canonical: https://daily.dev/posts/chatgpt-now-knows-what-you-do-on-other-websites-via-ad-collector-6ydoidhyl twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: ChatGPT now knows what you do on other websites via ad collector | daily.dev og:description: OpenAI's ad measurement system sets a cookie called __obi, scoped to .openai.com with SameSite=None, that gets sent back to OpenAI whenever a user visits any... og:url: https://daily.dev/posts/chatgpt-now-knows-what-you-do-on-other-websites-via-ad-collector-6ydoidhyl og:image: https://api.daily.dev/og/posts/6YDOidHyL.png og:image:alt: ChatGPT now knows what you do on other websites via ad collector og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # ChatGPT now knows what you do on other websites via ad collector **[Lobsters](https://daily.dev/sources/lobsters)** · 7 min read · 0 upvotes · 0 comments ## Summary OpenAI's ad measurement system sets a cookie called __obi, scoped to .openai.com with SameSite=None, that gets sent back to OpenAI whenever a user visits any site running OpenAI's advertiser pixel. The investigation reproduced the mechanism on a phone, traced the identifier from a signed JWT issued by ChatGPT's backend through a cross-site sync request, and observed it firing on sites like Chewy, Wayfair, ThriftBooks, Eventbrite, HelloFresh, Coursera and SeatGeek. The pixel also scrapes emails, phone numbers, and other identity fields from advertiser pages via hijacked tag-manager data layers, with scraped identity outnumbering advertiser-supplied identity in observed traffic. The mechanism works even for logged-out users via a persistent anonymous identifier, and only affects Chrome (not Safari or iOS browsers due to third-party cookie blocking). OpenAI's cookie policy classifies __obi as an analytics cookie despite it functioning as a cross-site marketing/ad-tracking identifier tied to ChatGPT accounts; OpenAI did not answer direct questions about this classification when contacted. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### What is the __obi cookie that OpenAI sets and why does it get sent to other websites? __obi is a cookie set by OpenAI's ad collector at bzr.openai.com, scoped to .openai.com with SameSite=None and Secure, which allows it to be attached to cross-site requests. It is created from a signed JWT issued by ChatGPT's backend that binds the identifier to a ChatGPT account or anonymous session, then gets sent to OpenAI whenever a page running OpenAI's advertiser conversion pixel loads, letting OpenAI link browsing on that site to a ChatGPT identity. _Anyone auditing third-party ad pixels for cross-site identity leaks can track findings like this on daily.dev._ ### Does OpenAI's ad tracking cookie __obi still work if a ChatGPT user is not logged in? Yes, the mechanism works for logged-out users. Across 932 decoded sync tokens, 736 carried subject_type account_user and 196 carried anonymous, and the anonymous subject proved just as stable as the account-linked one, persisting on a device for at least 27 days, meaning cross-site tracking continues even without an active login. _Developers weighing consent and identifier persistence in their own products can follow analysis like this on daily.dev._ ### Does OpenAI's advertiser pixel collect personal data like email and phone number from advertiser websites? Yes, the pixel SDK scrapes identity data directly from advertiser pages, not just from data advertisers deliberately supply. It hijacks the tag-manager data layer (window.dataLayer, adobeDataLayer, renamed GTM layers) to pull emails and phone numbers, and in observed traffic scraped identity events outnumbered advertiser-supplied ones 685 to 255; email, phone, and names are SHA-256 hashed, while country, region, city and postal code are sent unhashed. _Teams reviewing what their ad-pixel integrations actually collect can keep up with findings like this on daily.dev._ ## Community take How the wider developer community reacted, aggregated from 2 discussions and 728 comments across lobsters, hackernews (as of 2026-09-21). **TL;DR:** The discussion treats this as a predictably grim escalation of standard adtech surveillance onto an AI product, with heavy disgust at the normalization of tracking and a long, largely off-topic tangent about AI intelligence and propaganda. **Sentiment:** 5% positive · 15% mixed · 80% skeptical **The case for** - A few argue this is just standard ad-measurement partnership between companies that benefits ad relevance and isn't really 'spying'. - One commenter frames third-party cookie tracking as a decades-old accidental byproduct of early web specs rather than deliberate malice. **The pushback** - Many feel visceral discomfort ('icky') at adtech-style tracking being embedded in an AI chat product with no precedent. - Commenters argue this reflects a broader tragedy of private surveillance capitalism enabled by weak regulation and complicit engineers. - Some say classifying the tracking cookie as 'analytics' while it functions as a marketing identifier is a normalization tactic akin to euphemism. - Several blame individual engineers and workers for building tracking systems rather than excusing it as inevitable ('if I don't build it, someone else will'). **By community** - hackernews (heated): Initial reactions are strongly critical of OpenAI's ad-tracking mechanism, but the thread quickly spirals into an extended, contentious tangent debating AI intelligence, propaganda, and EU tech regulation. **Hottest debate:** Whether AI systems demonstrate genuine intelligence or are merely convincing pattern-matchers, a debate that consumed most of the thread and overshadowed the tracking story itself. **Open questions** - Whether OpenAI's classification of the __obi cookie as 'analytics' rather than advertising/tracking will face regulatory scrutiny. - Whether EU-style regulation can meaningfully curb this kind of cross-site tracking without stifling innovation, as debated by commenters. **Highlights** > To me, this quote just about sums it up: > The mechanism is standard adtech. What has no precedent is running it on an AI chat product. As someone who has been well aware of this mechanism for quite some time, I still feel icky anytime I re-read the details of it. What a time to be alive. > — [mavsman on hackernews · 6 comments](https://news.ycombinator.com/item?id=49777671) > Whenever I say something like “that’s a cool feature, but to do it you would have to build spyware”, everyone else is just like “the cat is out of the bag ¯\_(ツ)_/¯”. (I don’t build spyware, or work on projects that do). It blows my mind that people don’t care about the world they are building with this stuff. It’s a real tragedy of the commons. People see these collaborators from different wars and regimes and think “I’d stand up against the bad guy”… well I’ve got news for you if you build spyware, you are not the person you think you are. > — [clickety\_clack on hackernews · 6 comments](https://news.ycombinator.com/item?id=49777865) > Your issue is you are defining spyware too broadly. This is not spying on users, but rather 2 companies partnering and sharing data to result in either a better ads system or better understanding on how ads are performing. This is a positive value to society and the commons. Wasting space in a site or app with an ad that won't convert is the true tragedy of the commons. It's a waste of time and money for all parties involved. > — [charcircuit on hackernews · 2 comments](https://news.ycombinator.com/item?id=49778547) > "standard adtech" I hate stuff like this. Sometimes euphemisms are kind, like "senior citizen" instead of "old person". But this is an attempt to normalize bad behavior that is really quite terrible for society. > — [m463 on hackernews](https://news.ycombinator.com/item?id=49782981) > Yeah, this is just standard third-party cookie functionality, which has always been sketchy. It honestly seems like it was only possible by accident; browsers have long prevented sites from reading cookies from other domains, but it seems like the people working on early specs might not have considered the ramifications of being able to set cookies for domains other than your own. A couple decades ago it might have seemed like no one would have any reason to set a cookie they couldn't read. > — [saghm on hackernews · 1 comments](https://news.ycombinator.com/item?id=49782279) **Source threads** - [lobsters](https://lobste.rs/s/jbnmj9/chatgpt_now_knows_what_you_do_on_other) · 55 points · 5 comments - [hackernews](https://news.ycombinator.com/item?id=49776729) · 631 points · 723 comments ## Similar posts on daily.dev - [How ChatGPT serves ads. Here's the full attribution loop.](https://daily.dev/posts/how-chatgpt-serves-ads-here-s-the-full-attribution-loop--n31nsws5c) · Hacker News · 0 upvotes · 0 comments - [I didn't realize ChatGPT was serving ads until I dug into how it actually works](https://daily.dev/posts/i-didn-t-realize-chatgpt-was-serving-ads-until-i-dug-into-how-it-actually-works-iywrshaes) · XDA Developers · 2 upvotes · 0 comments --- Tags: [#openai](https://daily.dev/tags/openai), [#privacy](https://daily.dev/tags/privacy), [#chatgpt](https://daily.dev/tags/chatgpt) [View this post on daily.dev](https://daily.dev/posts/chatgpt-now-knows-what-you-do-on-other-websites-via-ad-collector-6ydoidhyl) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"ChatGPT now knows what you do on other websites via ad collector","url":"https://daily.dev/posts/chatgpt-now-knows-what-you-do-on-other-websites-via-ad-collector-6ydoidhyl","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/chatgpt-now-knows-what-you-do-on-other-websites-via-ad-collector-6ydoidhyl"},"datePublished":"2026-09-21T03:02:19.898Z","dateModified":"2026-09-21T14:33:35.452Z","description":"OpenAI's ad measurement system sets a cookie called __obi, scoped to .openai.com with SameSite=None, that gets sent back to OpenAI whenever a user visits any...","image":"https://media.daily.dev/image/upload/s--0_ODbtD2--/f_auto/v1722860399/public/Placeholder%2008","thumbnailUrl":"https://media.daily.dev/image/upload/s--0_ODbtD2--/f_auto/v1722860399/public/Placeholder%2008","isAccessibleForFree":true,"articleSection":"Lobsters","inLanguage":"en","publisher":{"@type":"Organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180}},"author":{"@type":"Organization","name":"Lobsters","logo":"https://media.daily.dev/image/upload/s--tl8v_Fku--/f_auto,t_logo/v1698841318/logos/lobste.jpg","url":"https://daily.dev/sources/lobsters"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/chatgpt-now-knows-what-you-do-on-other-websites-via-ad-collector-6ydoidhyl","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"openai,privacy,chatgpt","timeRequired":"PT7M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"Lobsters","item":"https://daily.dev/sources/lobsters"},{"@type":"ListItem","position":3,"name":"ChatGPT now knows what you do on other websites via ad collector"}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/chatgpt-now-knows-what-you-do-on-other-websites-via-ad-collector-6ydoidhyl#faq","mainEntity":[{"@type":"Question","name":"What is the __obi cookie that OpenAI sets and why does it get sent to other websites?","acceptedAnswer":{"@type":"Answer","text":"__obi is a cookie set by OpenAI's ad collector at bzr.openai.com, scoped to .openai.com with SameSite=None and Secure, which allows it to be attached to cross-site requests. 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