OpenAI published a technical post on Wednesday explaining how ChatGPT's advertising system actually works — and how big it has already become. The company says ChatGPT Ads passed $1 billion in annualized revenue run rate in under 200 days and has drawn more than 100,000 advertisers, the same week it expanded ads to 26 more countries for a total of 89.

Ad selection is run by a custom, post-trained frontier model OpenAI calls the orchestrator. It handles the whole flow through tool calls — choosing when to run retrieval, ranking, relevance scoring and auction steps — in a separate service, so it cannot slow down or shape ChatGPT's answers. Because conversational intent does not arrive as a single search-style request, the system keeps a stateful session across turns and even across conversations, rewrites that context into retrieval queries and semantic embeddings, fetches candidates with approximate-nearest-neighbor search, then filters for budget, pacing, policy, targeting and advertiser deduplication.

A day earlier, OpenAI had emailed advertisers that creative enhancements — automatic rewrites of ad headlines, text and landing pages — will be switched on by default for new and existing campaigns unless advertisers opt out. Ads appear only on the Free and Go plans; Plus, Pro and Enterprise users see none.