What to do when Ad Exchange renders wrong ad sizes?

Ad Exchange Ad Optimization
February 4, 2021 | by Kean Graham
What to do when Ad Exchange renders wrong ad sizes

As a publisher, you often do your regular checks on your site. On desktop, all ads seem to be loading correctly. Mobile seems fine, but then you scroll down and notice an oversized 300×250. A 414×345 is displayed on a medium rectangle ad slot instead of the 300×250 you initially wanted even after you’ve defined the size inventory for your mobile unit.

There have been several reports in forums and boards about Ad Exchange rendering the wrong ad size in mobile views. This has been attributed to the Ad Expansion feature on Google Ad Manager. Ad slots are expanded to the maximum allowed space for a mobile device to give it a more organic fit in the content. At the moment, it is only available to backfill display and out-stream video ad slots on the mobile web. Not all ad slots are eligible for expansion, though.

To uphold the ad’s aspect ratio, it may expand to the width of the device, while the height may be equal but only when appropriate. There are instances that it will not always fill to the device’s size in width and height. According to Google Support, these instances are:

  • Only expand to the container width. The container width is x, while the device width is greater than x.
  • Expand by width but not height.
  • Don’t expand at all.

You will see something similar to these:

What to do when Ad Exchange renders wrong ad sizes? MonitizeMore

The left image is the ad displaying your set inventory size, for example, 300×250. With the Ad expansion feature, the ad will appear like the image on the right, a 414×345.

The expansion will attempt to fit the device’s width, as long as the content is not being overlaid. According to Google Support:

  • If the overlap is detected with device width expansion but not with container width expansion, the container width will be used.
  • If the overlap is detected with both container width and device width expansion, the slot won’t be expanded at all.

This feature is enabled for all users, but being able to control (enable or disable) it is only available for paid accounts on Google Ad Manager 360. For non-paying users, Ad Contraction is the other feature you can control, which is the opposite of Ad Expansion. This allows smaller creatives to deliver other than the specified inventory size/s.

If you are using Google Ad Manager 360, you can disable this feature at the network level by:

  1. Signing-in to Google Ad Manager.
  2. Click Admin and then Global Settings and then Network Settings.
  3. Disable Ad expansion for mobile web under “Ad serving settings.”

What to do when Ad Exchange renders wrong ad sizes? MonitizeMore

For Unified Pricing Rules this is also applicable. However, if you have set-up size-specific rules, it will only apply to requested sizes. This means that if the ad comes back with an expanded size, your UPR will not apply.


Still not sure how to handle ads not rendering the correct size? How about sorting out any other ad optimization issues that are causing you to lose out on revenue? Let MonetizeMore help! Our ad ops teams can help solve any ad optimization issue and optimize your ad inventory for maximum revenue. Sign up to MonetizeMore now!

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