OpenAI signs Magnite and PubMatic deals to fill unused ChatGPT ad space

The Information reported on November 2, 2026 that OpenAI has signed deals with Magnite and PubMatic to fill unused ChatGPT ad space. The report, citing sources familiar with the deals, says the two companies’ platforms will let advertisers buy placements they could previously reach only through OpenAI directly or through its beta Ads Manager. An OpenAI spokesperson said the arrangements make it “easier for advertisers to buy and manage ChatGPT ads through tools they already use,” according to coverage of the report.

Magnite and PubMatic run sell-side platforms — the software that auctions a publisher’s available ad slots to advertisers in real time. Under these deals, they will handle what the industry calls remnant inventory: ad space OpenAI has not sold through direct deals. That distinction matters for how much money is at stake. Remnant inventory is, by definition, the space left over, and the people familiar with the deals told The Information that advertising volumes routed through Magnite and PubMatic remain small but are expected to grow quickly.

How advertisers will buy

Advertisers will use each platform to set spending budgets, submit bids and upload their ads, while OpenAI retains control over ad delivery, including where and how advertisements are displayed. The setup keeps the buying plumbing familiar — budgets, bids and creative uploads inside tools media buyers already operate — while the decision about what appears next to a ChatGPT answer stays with OpenAI. The agreements add partner buying routes alongside OpenAI’s beta Ads Manager, introduced in May, which gives businesses a self-service option to create and manage campaigns.

The two deals extend an ad infrastructure OpenAI has been assembling through partnerships with companies including Amazon Ads, Criteo, LiveRamp and StackAdapt, according to Seeking Alpha’s report on The Information’s story. For Magnite and PubMatic, both independent platforms that compete with Google’s AdX exchange, the deals add inventory from one of the most closely watched AI products in the world — even if the volume flowing through them starts small.

What the market made of it

Shares of Magnite rose about 13% and PubMatic rose nearly 10% after the report, Seeking Alpha reported. RBC Capital Markets maintained outperform ratings on both stocks, with price targets of $27 for Magnite and $20 for PubMatic, in a note that described the partnerships as a potential source of incremental growth for the two companies. A share-price jump on a report is not proof of how much revenue the deals will produce; it is a read on how much investors think the option is worth.

How ChatGPT ads got here

OpenAI began testing ads in ChatGPT in the United States on February 9, 2026, for logged-in adults using its Free and Go plans. As of October 21, those were the only plans carrying ads; Plus, Pro and Enterprise remained ad-free. OpenAI says ads are labeled, kept separate from ChatGPT’s answers and do not influence them, TokenPost reported.

The business has scaled fast from a small base. It was running at approximately $100 million in annualized revenue by March 2026 and reached a $1 billion annualized revenue run rate on August 31, according to Crypto Briefing’s account of the figures. An annualized run rate projects recent revenue across a full year; it is a snapshot of pace, not a tally of money collected over twelve months. By October 21, more than 100,000 advertisers had run campaigns, and ChatGPT ads were available in 89 countries.

What is still unknown

The financial terms of the Magnite and PubMatic partnerships were not disclosed, so it is unclear how revenue will be split or how much of ChatGPT’s inventory will flow through these channels. Nor is there a public timetable for when buying through the two platforms goes live at scale. The open question is whether advertisers already using Magnite and PubMatic actually spend through them on ChatGPT — the sources describe current volumes as small, and the deals will be judged on whether that changes, not on the signing itself.