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Real-Time Bidding

Last updated: January 23, 2024

About Open RTB

Real-time Bidding (RTB) is a way transacting media that allows an individual ad impression to be put up for bid in real-time. This is done through a programmatic on-the-spot auction, which is similar to how financial markets operate. RTB allows for Addressable Advertising; the ability to serve ads to consumers directly based on their demographic, psychographic, or behavioral attributes.

The Real-Time Bidding (RTB) Project, formerly known as the OpenRTB Consortium, assembled by technology leaders from both the Supply and Demand sides in November 2010 to develop a new API specification for companies interested in an open protocol for the automated trading of digital media across a broader range of platforms, devices, and advertising solutions. At the time Programmatic had only accounted for 4% of the display advertising market. By 2017, RTB is expected to account for 29% of the digital mix. *Source: eMarketer March 2013. This group continues to create open industry standards that ensure all parties, buy and sell side alike, can transact RTB at scale and build future industry innovation.

Previous Versions

The following table provides links to previous version of OpenRTB.

VersionRelease Date
OpenRTB v2.6-202309
Features include:
September 2023
OpenRTB v2.6-202303
Features include:

  • Object: Refresh The minimum exposure time, in seconds per view, that the (uninterrupted) ad creative will be rendered before refreshing to the next creative.

  • Object: RefSettings Information on how often and what triggers an ad slot being refreshed.

  • ${AUCTION_IMP_TS} in Substitution Macros to signal the timestamp when an impression was fulfilled (e.g. when the ad is displayed) for use by platforms that cannot fire a notification as soon as an impression takes place.

  • New plcmt attribute in Object:Video to support updated values for digital video definitions

  • Deprecation of placement attribute

  • Added implementation guide (.gif examples with definitions
    and Example code for publisher to signal both legacy definitions and updated definitions)

April 2023
OpenRTB v2.6-202211
Features include:

  • Process details for versioning, contributing, and monthly release cadence

  • A new object for DOOH and implementation guide

  • Inclusion of the GPP string and applicable section in regs object

  • Move inventorypartnerdomain out of ext and into site and app objects

November 2022
OpenRTB 2.6 (PDF)
OpenRTB 2.6 includes features to support CTV buying and selling. Release highlights include:

  • New attributes and guides for buying and selling Ad Pods

  • New objects to describe Channel & Network of content

  • Structured User-Agent object to support upcoming freezes to User-Agent string

  • Use of AdCOM 1.0 Lists for faster updates
April 2022
OpenRTB 3.0 (PDF)
OpenRTB 3.0 includes features to give buyers more transparency during the bid process. Release highlights include:

  • New process of cryptographically signed bid requests to view the actual path of inventory

  • New companion “Advertising Common Object Model” specifications (AdCOM)

  • Ad Management API Standard companion specification, standardizing the creative approval process for buyers and sellers, streamlining development efforts across platform integrations
September 2017
OpenRTB 2.5 (PDF)
OpenRTB 2.5 included updates that integrated industry trends and allowed for improvements in programmatic technology. Release highlights include:

  • IAB New Ad Portfolio Support – integrating flexible aspect-ratio based ads into the bid object

  • Video Placement Type Support – adding visibility into what type of placement a VAST (video ad serving template) tag is running in accordance to the IAB digital video glossary

  • Header Bidding Support – allowing for a signal when a bid request is originated from an upstream decisioning implementation like header bidding

  • Historic Metrics Support – whereby exchanges can pass historic metrics such as viewability or click through rate

December 2016
OpenRTB 2.4 (PDF)
OpenRTB 2.4 main improvements:

  • Video skippability support

  • SSL Support

  • New audio object created

  • Increased location support

March 2016
OpenRTB 2.3.1 (PDF)
Provided an update to the specification addressing two typos:

  • Section 3.2.13 - in the user object, the buyer ID attribute has been corrected to "buyeruid."

  • Section 4.4 - The ${AUCTION_BID_ID} macro has been corrected to be substituted with the “BidResponse.bidid” attribute.

June 2015
OpenRTB 2.3(PDF)
The OpenRTB 2.3 specification was the first version updated to provide support for native ads. This was one of the most significant updates to OpenRTB as it allows for native ads to be targeted, optimized, and transacted on programmatically, reducing workload on publishers and advertisers alike. Release highlights include:

  • Native ad placements must be included directly into the impression object in order to be passed through the bidstream.

  • Allows for the inclusion of metadata (title, urls, data, img files) in the native request. The buy side now has the ability to describe the unit that’s being bid on and the supply side is able to define which fields are available and required in order to assemble the native ad.

  • Updates to the style of the document including improved diagrams and revamped table format to support the continued commitment to OpenRTB.

January 2015
OpenRTB 2.2(PDF)
OpenRTB 2.2 provided for improved PMP and non-intentional traffic support. With bot traffic becoming an increasing concern to both the buy and sell sides, OpenRTB 2.2 allows for all parties to be able to provide real-time feedback on ads to determine and block non-human traffic. Release highlights include:

  • Support to the allow for the differentiation of secure and nonsecure inventory

  • Exhaustive Deal ID support for Private Marketplaces

  • Improved backing for new types of mobile and video inventory

  • Ability for buyers to alert sellers in real time about suspected bot traffic

  • COPPA regulation support

April 2014
OpenRTB 2.1 (PDF)
OpenRTB 2.1 provided for improved VAST video, tablet and location targeting support. Release highlights include:

  • IAB Tier-2 category support

  • Recognition of tablet inventory
  • VAST video across RTB; the video object must represent an impression as either banner, video or both
  • Location source support; differentiation of GPS derived and zip code value targeting

October 2012
OpenRTB 2.0 (PDF)
OpenRTB 2.0 provided unified support for display, mobile, and video capabilities. This was a significant step forward for programmatic as allows for the harmonization of mobile and desktop advertising. Release highlights include:

  • VAST ad unit support

  • Improved geographical data definition

  • Increased cross-channel support for mobile and desktop through a common API language

  • Improved 3rd party data segment support for audience targeting

  • Enhanced attribution support; inclusion of device IDs in mobile & mobile app parameters

January 2012

Supporting Resources


IAB Tech Lab’s GitHub offers a reference implementation.

Related Documents

The following press releases and blog posts provide more information on OpenRTB.


If you have questions about OpenRTB, send an email to support to create a ticket.

IAB Tech Lab Contact

Hillary Slattery, Director of Programmatic, Product