28 Apr 2026

OpenAI's ad platform has two halves. On the ChatGPT side, the backend injects structured single_advertiser_ad_unit objects into the conversation SSE stream while the model is responding. On the merchant side, a tracking SDK called OAIQ runs in the visitor's browser and reports product views back to OpenAI. The two are tied together by Fernet-encrypted click tokens, four of them per ad.

I captured both halves on a consented mobile-traffic research fleet. Everything below comes from observed traffic.

When you send a message to ChatGPT, the backend opens an SSE response at chatgpt.com/backend-api/f/conversation . Most events in that stream are model-output. Some are ad units.…