Medium rectangle (300x250) display ad unit runs on 84% of sites listed in

The Medium Rectangle 300x250 ad unit has replaced the Leaderboard as the most popular display ad size running on websites*. It’s appearing on the greatest number of websites and makes up about 19% of all ads currently running on these sites. The Leaderboard took the second spot on the list with the Wide Skyscraper rounding out the top three. These sizes make up about 48% of all ads running on listed websites, while the ad sizes beyond the top 10 make up about 1/4 of all ads running online in November, demonstrating the long tail of display ad sizes. See chart above for more detail.

Additionally, both the medium rectangle and leaderboard ad units can be seen on about 84% of websites listed in Although there are dozens of ad sizes running on the Web, there are still a finite number of extremely common sizes. For example, the Button 1 (120x90) is the 10th most popular size, but it only runs on 9% of sites.

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*Research Methodology:  Kantar Media SRDS uses third-party real-time technology to detect the ad units and formats running on websites that accept advertising at various times during a given time period. This analysis was conducted by applying this technology to 15,799 websites (and 60,010 online ads) during November 2013.

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