Programmatic
OpenRTB
OpenRTB is the open technical standard, maintained by IAB Tech Lab, that defines how bid requests and bid responses are formatted and exchanged in real-time bidding.
OpenRTB is the shared language that lets thousands of ad tech companies trade with each other. Without it, every SSP and DSP would have to build a custom connection to every partner. The standard defines the objects in a bid request (impression, site or app, device, user, regulations, supply chain) and a bid response, plus rules for auctions and notifications.
It was first published in the early 2010s and is maintained by the IAB Tech Lab. Version 2.5 became the workhorse of the industry, and 2.6 (2022) added better support for CTV and ad pods, among other features. OpenRTB 3.0, which split the protocol into layers with the AdCOM object model, was released in 2018 but saw limited adoption, so most traffic still runs on 2.x.
OpenRTB also carries the industry's supply-chain transparency: the supplyChain object and fields that tie into ads.txt and sellers.json. Extensions cover native ads (native advertising), DOOH and more.
Think of it like this
OpenRTB is like the standard shipping container: because every port and ship agrees on the same box size, goods move across the world without repacking.
An example
A new SSP in Brazil that speaks OpenRTB 2.6 can connect to a global DSP in weeks rather than months, because both sides already understand the same fields.
Related terms
Real-time bidding (RTB)
Real-time bidding (RTB) is an automated auction in which advertisers bid on a single ad impression in the fraction of a second while a web page, app or stream is loading.
Bid request
A bid request is the message an SSP or exchange sends to potential buyers describing an available ad impression, inviting them to bid on it in a real-time auction.
Bid response
A bid response is a buyer's reply to a bid request, containing its offered price and the ad (or a link to it) to show if it wins.
IAB Tech Lab
IAB Tech Lab is the non-profit standards body for digital advertising technology, founded in 2014, which develops specifications such as OpenRTB, VAST, ads.txt, sellers.json and the Open Measurement SDK.
SupplyChain object (schain)
The SupplyChain object (schain) is a field in OpenRTB bid requests that lists, in order, every seller or intermediary that handled the impression on its way from the publisher to the buyer.
Sources: IAB Tech Lab: OpenRTB