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Real-time bidding (RTB) is a method of transferring media on an individual impression basis, which is bid on in real time via an ‘auction’. OpenRTB is an open protocol to automate trading of digital media. 

How it Works

Exchange or Supply Side Platforms (SSPs), also known as “inventory sources”, generate “bid requests” when a publisher wishes to fill an impression. Bids on those requests are submitted by Demand Side Platforms (DSPs) and the winning bid is decided by the inventory source. The corresponding advertisement for the winning bid is served to the browser or app that triggered the bid request.

DSPs can have integrations with multiple inventory sources to allow them to buy media programmatically from a wide variety of publishers. In order to transact with the inventory source, the DSP needs to understand how to read that given inventory source’s bid request object and also respond in a way that the inventory source can interpret. For this reason, the IAB released a standardised method for structuring bid requests which allows platforms to integrate more easily. These protocol standards aim to simplify the connection between suppliers of publisher inventory (i.e. exchanges/SSPs) and the buyers (i.e. bidders, DSPs).

Beeswax generally supports OpenRTB 2.3, but in some cases, fields from OpenRTB 2.5 are supported.

OpenRTB Basics

• The base of the protocol between an exchange and its bidder is HTTP
• JSON is the suggested format for bid request and bid response data payloads
• RTB transactions are initiated when an exchange or other supply source sends a bid request to a bidder
• Attributes are “required” if their omission would technically break the protocol
• Some optional attributes are denoted “recommended” due to their elevated business importance

Bid Requests

• The top-level bid request object contains a globally unique bid request or auction ID
• Must have at least one impression object
• id and imp (impression) are required objects 
• Bid Requests can also include additional objects that provide more information for the buyer e.g. site or app

Bid Response

• RTB responses contain bids that reference specific impressions within a bid request
• An empty HTTP response constitutes a no-bid 
• A bid response may contain bids from multiple “seats” or from the same “seat”. A seat generally corresponds to a customer of the DSP.
• Objects in a Bid Response include: BidResponse, SeatBid, Bid

Summary of Previous Versions

• OpenRTB 2.0 provided unified support for display, mobile, and video capabilities
• OpenRTB 2.1 provided for improved VAST video, tablet and location targeting support
• OpenRTB 2.2 provided for improved PMP and non-intentional traffic support
• OpenRTB 2.3 specification provides support for native ads
• OpenRTB 2.4 introduces a brand new advertising medium to the protocol: digital audio
• OpenRTB 2.5 includes updates that integrate current trends and allows for improvements in programmatic technology

Glossary of Common RTB Terms

Protocol - A protocol is a standard set of rules that allow electronic devices to communicate with each other.

IAB - Interactive Advertising Bureau. The organization which empowers the media and marketing industries to excel in the digital economy. 

Protobuf - Protocol Buffers. A method of serializing structured data. It is useful in developing programs to communicate with each other over a wire or for storing data.

VAST - Video Ad Serving Template. A document format that gives video players information about which ad to play, how the ad should display, how long it should play, and whether users are able to skip it, among other values.

PMP - Private MarketPlace. An invite-only marketplace where high caliber publishers offer their ad inventory to a selected group of advertisers.

DSP - Demand Side Platform. A system that allows buyers of digital advertising inventory to manage multiple ad exchange and data platform accounts through one interface.

SSP - Supply Side Platform. A system that allows web publishers and digital out-of-home media owners to manage their advertising space inventory, fill it with ads, and receive revenue. This term is largely synonymous with "Exchange".

HTTP - Hypertext Transfer Protocol. The protocol used for communication over a computer network and the most commonly used protocol for the internet. HTTPS is the secure version of HTTP.

JSON - JavaScript Object Notation. A minimal, readable format for structuring data. It is used primarily to transmit data between a web server and web client, as an alternative to XML.

XML - XML stands for eXtensible Markup Language. XML is a markup language like HTML. XML was designed to store and transport data.

RTB - Real-time bidding. A method of advertising inventory which is bought and sold on a per-impression basis, via programmatic instantaneous auction, similar to financial markets.

Impression - A term that refers to the point in which an ad is viewed once by a visitor, or displayed once on a web page.