You can control which creative sizes fill your ad slots using ad contraction. The new ad size does not necessarily match the full width or height of the ad slot. When this happens, the size of the similar ad is modified (using advanced imaging techniques) if needed and then served in the ad slot. To help increase competition for a particular ad size, we might substitute a text ad or similar-sized display ad to appear within the ad slot. Need optimization support? Reach out to a Google Certified Publishing Partner, experts at helping publishers monetize content.
