OpenRTB
The industry specification that defines how bid requests and bid responses are structured in real-time bidding.
What is OpenRTB?
OpenRTB is the technical specification, maintained by the IAB Tech Lab, that standardises communication between sellers and buyers in real-time bidding. It sets out the fields a bid request may contain, such as the impression, site or app, device, user signals, privacy flags and any deal IDs, and the structure of the bid response, such as price, creative markup and advertiser domain. Because nearly all exchanges, SSPs and DSPs support it, a buyer can connect to many sellers without a separate format for each. The specification has gone through several versions and now works alongside related standards such as the SupplyChain object and AdCOM.
How OpenRTB works
A seller’s system sends a bid request describing the impression. Buyers reply with bid responses in the same format, and the auction selects a winner.
- A seller platform builds a bid request in the OpenRTB format, describing the impression and its context.
- The request is sent to connected buyers, usually as JSON over HTTP.
- Each buyer evaluates the request and returns a bid response with a price and creative, or declines to bid.
- The seller selects a winner and notifies the buyer through win and loss notifications.
Why it matters
A common format lets any compliant buyer transact with any compliant seller. Deals are carried in the same messages, identified by a deal ID.
For adtech platforms
Supporting OpenRTB is the baseline for connecting to programmatic partners; it reduces integration work to agreeing which optional fields and extensions to use.
For advertisers
The richness of the fields a seller fills in determines how well a buyer can target and value each impression.
Practical example
An exchange sends an OpenRTB request for a video impression; three buyers respond and the highest eligible bid wins.
Key considerations
- Many fields are optional and platforms add their own extensions, so two OpenRTB integrations can still behave differently.
- Privacy and consent signals travel inside the request, and both sides must respect them.
- Fields that support supply-chain transparency, such as the SupplyChain object, only help if every intermediary populates them.
More Advertising Technology terms
Frequently asked questions
Who maintains OpenRTB?
The IAB Tech Lab, an industry standards body, publishes and updates the specification.
What is the difference between RTB and OpenRTB?
RTB is the auction process itself; OpenRTB is the standard message format that most platforms use to run it.
Are deals carried in OpenRTB?
Yes. PMP and programmatic guaranteed deals are passed in the request with their deal IDs, so buyers know which agreement applies.
Does OpenRTB cover native and video?
Yes. The request can describe banner, video, audio and native impressions, with separate objects for each format.