nurl

nurl is the win notice URL in an OpenRTB bid: the address the exchange calls when the bid wins, telling the bidder it won and at what price, and optionally returning the ad markup.

The bidder puts the URL in the nurl field of each Bid object. OpenRTB 2.6 is careful about what a win means: the notice does not by itself show that the ad was delivered, viewed or billable (IAB Tech Lab, OpenRTB 2.6, section 4.2.3). Before calling it, the exchange replaces macros such as ${AUCTION_PRICE} with real values, so the bidder learns the clearing price.

The win notice can also serve the ad. The bidder may return the creative in the bid's adm field or deliver it in response to the win notice; if both carry markup, adm wins. Serving on the win notice keeps bid responses small but adds a round trip before rendering.

Because a win can still fail to render, OpenRTB 2.5 added a separate billing notice, burl. Buyers who count spend on nurl overcount whenever the page closes or the publisher's ad server picks another ad. The OpenRTB notes on digital out-of-home make the same split, firing nurl at the win and burl once the creative is on screen.

Example: A DSP bids with "nurl": "https://dsp.example/win?id=${AUCTION_ID}&p=${AUCTION_PRICE}". It wins at $2.35, so the exchange calls https://dsp.example/win?id=8f2c&p=2.35. The DSP logs the win and waits for the billing notice before it books spend.

Related terms: burl, loss notification, bid response, OpenRTB, real-time bidding.

Authoritative source: IAB Tech Lab, OpenRTB 2.6, section 4.2.3 "Object: Bid", field nurl (accessed 9 November 2026).

Read the full guide: OpenRTB 2.6 explained: bid request anatomy, field by field.