What is Video Ad Serving Template (VAST)

The Video Ad Serving Template is an IAB standard and supports and extends upon the features of VAST 2 with enhancements over earlier versions, which includes-

  • Multiple ads can be supported in a single VAST response, which includes-

Standardized ad pod responses like optimized pods

Skippable linear ads, which include network-level custom skip times

Fallback, which is popularly known as waterfall.

  • Granular VAST 3 error code
  • Supports adaptive bitrate creatives and provides the best quality video stream per bandwidth and processing speed
  • Alternative companion creatives, available with both the iOS IMA SDK and HTML5 IMA SDK
  • Icons available with the HTML5 IMA SDK

How can you enable VAST 3 for your network?

A network setting controls the default VAST version, which does away with the need to retag for this version or the future ones.

How to update your network VAST setting?

  1. In Ad Manager, click on Admin, then Video, and then on Video Settings.
  2. As the “VAST version,” select VAST 3.

output=vast should be requested by tags to use the version set as your default network.

You should make sure that the players are capable of processing XML responses for whatever version you choose.

If IMA SDK is used for your video player, output=xml_vast4 will always be set as the output parameter for the video ad request. No reliability risk is posed as backward compatibility of the SDK is ensured with all VAST versions that any third-party ad server may serve.

With output=xml_vast3, you can request VAST 3 for specific ad tags or parts of your site if you do not use the IMA SDK.

How to do customizations of skippable and engaged view time?

For your directly sold skippable ads, you are provided an option by VAST 3 to customize the “Skip” and “Engaged view” times. This is, however, completely unrelated to skippable ads served through Ad Exchange.

How to customize and skip engaged view times?

  1. In Ad Manager, click on Admin > Video>  Video Settings.
  2. Make adjustments to the following settings-
  • Skippable skin time- The duration of time, in seconds, must be spent by the user, watching skippable video ads, before the ability to skip it.
  • Skippable view time- The duration in seconds, for which a user must watch a skippable ad before an engaged view is considered.

Recommendations for VAST 3-

  • IMA SDK or another VAST 3-compliant player: Upto VAST 4 is supported by IMA SDK and is advisable for SDK for VAST players and other Ad Manager features.
  • GPT: Use Google Publisher Tags to render display companion ads served with VAST 3.

About VAST 4-

You can find support for up to VAST 4.2 by Ad Manager. You should use the latest available version to enjoy all the features.

VAST 4.x version highlights-


  • Support for Secure Interactive Media Interface Definition (SIMID), which might for interactivity replace VPAID
  • Allows multiple UniversalAdID nodes
  • Extra macro support for Ad Break Info


  • Merges VAST with Audio Ad Serving Template
  • Initial changes to begin deprecation of VPAID
  • Standardizes close captioning files


  • Supports  high-quality mezzanine files
  • Supports universal ad ID programs
  • Extra VAST video error codes for server-side ad insertion and mezzanine files
  • Additional VAST video error codes for server-side ad insertion and mezzanine files

The support for VAST 4 is extended to Ad Exchange publishers. Bid requests include the VideoProtocol field, which specified accepted VAST versions available for RTB and Open RTB. For all the features released in VAST 3, continued support is provided by VAST 4.

How to enable VAST 4 for your network?

A network setting controls the VAST version. The network is set to serve VAST 3 by default. To start doing VAST 4, the network setting requires an update recommended to begin serving the version without a need to retag automatically.

Update your network settings-

  1. Sign into Google Ad Manager and click on Admin Video.
  2. For the “VAST version,” select VAST 4.

Your video ad tags simply request output=vast, and the Ad Manager uses the VAST version set in your network default. For specific ad tags or parts of your site, you can request a VAST version via the following-

  • VAST 4: output=xml_vast4
  • VAST 3: output=xml_vast3
  • VAST 2: output=xml_vast2

How to manage Ad Manager or externally hosted mezzanine files?

A mezzanine file is a designation for a creative video file when you create a new linear video creative. This file should be a high-quality video file that acts as a source to develop other versions of a creative and is optimized for varying devices and formats.

If you wish to designate a video file as a mezzanine file, you have to-

  1. Sign into Google Ad Manager and follow the instructions to add a linear creative set to a video line item
  2.  Designate your creative file as a mezzanine file-

For Ad Manager-hosted assets, select Store uploaded file as mezzanine and either use drag and drop or upload a new asset.

For assets that are externally hosted, enter an assent URL and click on Ad Assets and choose to store the file as a mezzanine.

How to set an ad ID for linear video creatives?

On creating a new linear video creative, a universal ad ID can be set, which allows for standardized tracking for different video creatives. Additionally, you can choose the identification registry, such as ad-id.org or clearcast.co.uk.

If you wish to set an ad ID or select a registry-

  1. Sign into Google Ad Manager and follow the instructions to add a linear creative set to a video line item.
  2. When the optional settings are being configured, put in your ad ID and optional registry.

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