Google AdSense Expands Serving Smaller Ads In Larger Ad Units

Google is expanding its practice of serving a similar-sized display ad in a larger ad format in order to increase competition for AdSense ad space. Google now allows the 336×280 ad unit to serve 300×250 ads.

When the smaller ads are served they float in the center of the ad format as shown in the example below. 

Google first allowed smaller ad creative to run in larger ad units with the  introduction of the 300×600 and the 970×90 ad sizes to AdSense earlier this year. Google said it would allow 160×600 ads to display in the 300×600 unit and 728×90 ads to run in the 970×90 unit due to the lack of available creative in the new sizes.

Publishers can opt out of having similar-sized display ads served in ad units from the Allow & Block Ads tab in your account. Note that opting out applies at the account level rather than on an individual ad unit.