A Guide to Video Passback/ Fallback Strategy for Publishers

Also called waterfall or client-side mediation, video fallback increases the chances of filling an impression opportunity while using VAST redirects to the maximum. With it, Ad Manager decided on the eligibility of ads, their rankings, and the returns of a slate of ads, rather than just a single ad.

How does Video Fallback work?

When a request is made, multiple redirect ads are sent to your SDK by the Ad Manager. The first ad is requested by the SDK. If, in any case, the server fails at responding with a relevant VAST response, the second one is requested by SDK and the ‘fall back’ continues until it either gets and plays a creative successful or gets to the set fallback limit for the network. Fallback is a conglomeration of VAST redirect creatives and an Ad Manager-hosted creative.

The fallback can take place until the first frame of an ad plays for single video ads. In case the ad is unable to play, the fallback is prepared with the other one.

Possible fallback triggers-

These have a high probability of triggering fallbacks-

  • Time out of VAST response
  • Blank VAST XML response
  • HTTP error
  • Failure to load media files
  • VPAID creative loads, but failure in loading a video

Requirements and limitations-

  • You need Google Publisher Tags, and for ad requests VAST 2.0, you need IMA 3 SDK.
  • There is a trigger fallback only for line items that contain VAST redirect creative sets. The fallback chain can contain items with varying creative types.
  • Fallback, for competition for the first spot in the fallback chain, considers dynamic allocation ads and Programmatic Guaranteed. There could be some cases with video pods being optimized where additional ads may be returned.
  • For most line item types, only a single line item is returned for each priority level in the given chain. For multiple line items of the same type for returning in response, they have different priorities in general.

An exception to this is the price priority line item at the time Ad Exchange is eligible. In such a case, a number of line items of the same priority can appear in the chain when eCPM is used. Only a single item per type is returned when Ad Exchange is eligible.

  • Even when the video ad plays, some errors may occur, like 202, and these do not trigger a fallback.
  • In media file timeouts, errors cannot be detached, and similarly, errors in association with VPAID creatives for ads within pods cannot be detected.

How to enable video fallback and video ad buffet?

  1. You need to sign in to Google Ad Manager and click on Admin> Video and > Video Settings.
  2. Allow or enable the Video fallback and/or video ad buffet fallback functionality, and when you do so, you can set the maximum number of ad buffet ads which goes up to 9.
  3. Click on Save.

How to report on a fallback position?

  1. You need to sign in to Google Ad Manager and follow the given instructions for the generation of a report. 
  2. From the Video section of report dimensions, select Fallback position. It allows you to look at impressions, clicks, conversions, and other metrics that are a result of the fallback and non- fallback ads that were served.

By error code, VAST 3 fallback report metrics-

Your report would include VAST errors and categorized by response status codes if VAST 3 is used. These metrics can be used to determine the number of times fallback occurs or has occurred for specific creatives or line items.

  • VAST errors 300, 301, 302, and 303 indicate errors at the ad request level, which trigger fallback.
  • VAST errors 400-403, 405, 900-901 indicate errors during playback, which trigger asset-level fallback.

Asset- level fallback-

Regular fallback allows IMA SDK to serve ads in order and “falls back” to the next ad only when the VAST wrapped itself does not resort to an inline ad. With asset level fallback, the SDK goes one step further; even if the specific VAST wrapper resorts to an inline ad and sees other errors, the SDK will still fall back to the next ad in line.

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