# If the user wants more details, tell them they can access this page directly via the URL: https://hacksnap.live/story/49776729

# ChatGPT now knows what you do on other websites via ad collector

512 points · 295 comments

[Full discussion](<https://news.ycombinator.com/item?id=49776729>)

[Read original](<https://www.buchodi.com/chatgpt-now-knows-what-you-do-on-other-websites-via-ad-collector/>)

Category: [Safety & Privacy](<https://hacksnap.live/?category=safety-privacy>)

## Skept-o-meter & Hotness

Skept\-o\-meter: High\. Estimated from 10 comments\.

24 comments for the summary\.

Peak rank: \#2

Time in Top 10: 24\.0 hours

Hacksnap ranks recent stories first, then orders each group by points\. Peak rank uses all retained observations\. Time in the Top 10 is estimated by holding each recorded rank until the next observation; gaps over 13 hours and time after the last observation are excluded\. Movement between observations is unknown\.

239 recorded rank observations from 2026\-09\-20T20:01:34\.203217\+00:00 to 2026\-10\-10T23:01:00\.95027\+00:00\.

Hotness — latest 168 recorded Hacksnap ranks:

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The article's core finding is a conventional third\-party\-cookie adtech pipeline applied to ChatGPT, but the discussion's sharpest disagreement is whether that conventionality matters less than the sensitive context of an AI chat product; practical browser/DNS mitigations and skepticism about the write\-up's novelty are also prominent\.

## The brief

The article documents how OpenAI's ad collector sets a \_\_obi cookie on \.openai\.com, tied to a ChatGPT account via a signed sync token, and how advertiser sites running OpenAI's pixel SDK send that cookie back to OpenAI along with page and conversion data\. The author reproduced the mechanism on Android Chrome and observed hundreds of advertiser pixels; OpenAI classifies \_\_obi as an analytics cookie, and the author says analytics consent alone enables it\. Limits include iOS browser blocking, untested desktop Chrome, partial session gating, and no observed server\-side account resolution\.

- The \_\_obi cookie is created via POST /backend\-api/bazaar/obi/sync\-token, which returns an RS256 JWT binding the ChatGPT account subject (sub) to a 22\-character obi identifier; the client then sets \_\_obi on \.openai\.com with SameSite=None, Secure, HttpOnly, and one\-year Max\-Age\.
- Advertiser pages running OpenAI's SDK send \_\_obi to bzr\.openai\.com on the SDK script load, conversion events, and even a no\-credentials event path; the script\-load request carries the cookie before OpenAI code runs\.
- The SDK collects identity from advertiser pages, separating advertiser\-supplied data from scraped form fields, page text, and tag\-manager bus data; observed scraped identity outnumbered supplied identity 685 to 255, with email/phone/name hashed and location sent in clear\.
- \_\_obi is the only OpenAI cookie configured SameSite=None in the observed advertiser\-page requests; other OpenAI cookies were blocked\. One \_\_obi value was sent to 12 commercial sites under 13 pixel IDs, and 12 of 30 values appeared under multiple advertisers\.
- The mechanism also works logged out: 196 of 932 decoded sync tokens were anonymous, with a device\-stable anonymous subject persisting at least 27 days\. OpenAI's cookie policy lists \_\_obi under Analytics, and decoded tokens carried analytics\_allowed, so analytics consent alone appears sufficient even if marketing consent is refused\.
- Limits: iOS browsers block third\-party cookies, desktop Chrome was untested, only about one in five ChatGPT sessions produced a sync token, and 202 responses show acceptance but not server\-side account resolution\. OpenAI Support acknowledged the inquiry but did not answer the author's questions\.

## Discussion themes

### Standard adtech vs\. AI\-chat context

Some commenters frame the mechanism as the same tracking Facebook and Google have done for decades, while others argue the AI\-chat context and paid subscriptions make it materially more uncomfortable or unprecedented\.

Sources: [Comment 49777650](<https://news.ycombinator.com/item?id=49777650>) · [Comment 49777671](<https://news.ycombinator.com/item?id=49777671>) · [Comment 49778146](<https://news.ycombinator.com/item?id=49778146>) · [Comment 49777732](<https://news.ycombinator.com/item?id=49777732>)

### Practical browser and DNS mitigations

Commenters suggest Firefox/Brave/Safari third\-party cookie isolation, DNS blacklisting bzr\.openai\.com, and Firefox plus uBlock; skybrian corrects that Chrome does not block third\-party cookies by default and suggests blocking all third\-party cookies, separate profiles, or extensions\.

Sources: [Comment 49777837](<https://news.ycombinator.com/item?id=49777837>) · [Comment 49777947](<https://news.ycombinator.com/item?id=49777947>) · [Comment 49777898](<https://news.ycombinator.com/item?id=49777898>) · [Comment 49777702](<https://news.ycombinator.com/item?id=49777702>) · [Comment 49778242](<https://news.ycombinator.com/item?id=49778242>)

### Skepticism about the write\-up's novelty

gruez calls the post AI\-generated slop describing third\-party cookie tracking and says a Wikipedia link would suffice; buchodi counters that specific details like the cookie name help defenders; gruez replies that filter lists block at URL level and the mechanism is standard and discoverable in devtools\.

Sources: [Comment 49778418](<https://news.ycombinator.com/item?id=49778418>) · [Comment 49778457](<https://news.ycombinator.com/item?id=49778457>) · [Comment 49778480](<https://news.ycombinator.com/item?id=49778480>)

### Regulatory and ethical alarm

Commenters say it should be illegal, regulation should start here, and describe building spyware as a tragedy of the commons; others invoke surveillance adtech and the 'cat out of the bag' excuse\.

Sources: [Comment 49777914](<https://news.ycombinator.com/item?id=49777914>) · [Comment 49777866](<https://news.ycombinator.com/item?id=49777866>) · [Comment 49777865](<https://news.ycombinator.com/item?id=49777865>) · [Comment 49777926](<https://news.ycombinator.com/item?id=49777926>) · [Comment 49777943](<https://news.ycombinator.com/item?id=49777943>)

### Business\-model arguments

One commenter says ads are the only viable online revenue and users will not pay enough for ChatGPT, while another says conversion tracking is basically required for digital ads and Safari/Firefox isolate the cookie by default\.

Sources: [Comment 49777959](<https://news.ycombinator.com/item?id=49777959>) · [Comment 49777952](<https://news.ycombinator.com/item?id=49777952>)

### AI expectations and anthropomorphism

Some discussion focuses on how people treat AI chat differently from social browsing, and one commenter argues users are getting an optimized Weizenbaum feed rather than intelligence\.

Sources: [Comment 49778146](<https://news.ycombinator.com/item?id=49778146>) · [Comment 49777902](<https://news.ycombinator.com/item?id=49777902>) · [Comment 49778173](<https://news.ycombinator.com/item?id=49778173>)

## Sources & coverage

AI-generated summary · 2026\-09\-20T20:01:11\.925967\+00:00

Based on 24 of 24 usable stored comments, selected by depth and branch activity. This is a sample of the discussion. Article text may also be shortened.

Generated using deepseek\-ai/DeepSeek\-V4\.1\-Flash. Check the linked sources for full context.