Best Ad Sizes for Web Publishers [Research Data]

As a publisher, you typically start with a standard set of ad sizes — regardless of the way you chose to monetize the site. And, that’s the right move. IAB standard ad sizes have higher demands, this, in turn, leads to better competition and higher eCPM. But why not go a step further? Do you know what are the best IAB standard ad sizes?   

Apparently, you might be running some of them. However, understanding the best ad sizes lets you prioritize your stack, discover new ad sizes (that you’ve overlooked), and most importantly, deliver a better user experience by cutting down on the lowest-performing sizes. Without any further ado, let’s dive in. 

Sidenote: By ad sizes, we mean the sizes of the ad creatives delivered from Ad Manager or Ad Exchange, not the creative size configured on a line item.

Methodology: We analyzed over 700 million desktop ad impressions and ~1.5 billion mobile ad impressions across all the geographies and browsers. The impressions are spread across ~ 200 web properties and we have only included sites with more than a million unique pageviews per mo. We have employed a basic data cleaning method to remove the noises (non-standard sizes) in the datasets. 

Most In-demand Display Ad Sizes

Mobile: 

We knew that mobile leaderboards and medium rectangles are the most common ad sizes. But this is quite surprising — 320×50 and 300×250 accounted for more than 80% of the total impressions delivered. 

And, it makes sense as mobile screens can’t accommodate vertical and larger ad units. Besides, these two sizes perfectly fit in across all the pages on mobile. 

Most In-Demand Display Ad Sizes - Mobile

Ad Size (delivered) % of Total Impressions
320×50 52.16
300×250 34.37
300×600 2.92
320×100 2.92
336×280 2.90
375×250 1.43
360×50 1.19
375×312 1.07
400×50 1.04

Desktop: 

When it comes to desktop, medium rectangle, leaderboard, and vertical units are the most common ad sizes.

What’s interesting is that it shows the ad layouts of the publishers aren’t really different from one another. A leaderboard is either at the top or bottom (sticky), medium rectangles are within the page content, and vertical ad units are on the sidebar. 

As a publisher can easily deliver a single leaderboard/vertical/medium rectangle unit, all of them make up to 20% – 25% of the impressions each.

Note: Based on the layout, 320×50, dubbed as a “mobile leaderboard” can be used on the desktop as well. Sidebar, in-article placements can render both 320×50 and 300×250 depending on the availability of the demand*. Also, publishers can render such smaller units inside their chatbots.

*You can use 320×50 along with 300×250. If you send multi-size ad requests and have multi-size pricing set in place, then you can deliver the highest paying ad while ensuring a better fill rate. 

Most In-demand Display Ad Sizes - Desktop

Ad Size (delivered) % of Total Impressions
728×90 25.68
160×600 21.61
300×250 21.52
300×600 13.24
320×50 10.86
970×250 2.59
320×100 1.70
336×280 1.55
970×90 1.25

Highest Earning Ad Sizes

Mobile:

As expected,  more than 80% of the revenue is from 320×50 and 300×250 units. After they make up most of the impressions on mobile. 

Highest Earning Ad Sizes - Mobile

Ad Size (delivered) % of Total Revenue
320×50 48.64
300×250 41.19
320×100 1.54
336×280 2.30
375×250 1.84
360×50 1.02
375×312 2.29
400×50 1.19

Desktop: 

As you could see, 728×90 (Desktop leaderboard) gets more revenue for publishers. It makes sense as it is placed ATF (higher viewability) and has better CTR (we’ll get to this part later). 

Highest Earning Ad Sizes - Desktop

Ad Size (delivered) % of Total Revenue
728×90 21.56
300×600 19.55
300×250 19.25
160×600 17.79
320×50 9.05
970×250 8.36
336×280 2.31
970×90 1.25
320×100 0.88

Best Ad Sizes (based on eCPM)

Mobile:

The trend is pretty clear — larger the size, better the CTR, and higher the eCPM.

There’s only one exception. 336×280 has a better CTR, but eCPM isn’t higher. The reason might be viewability or lack of demand for the unit. From the previous graph, we know that it accounts for just 3% of the total impressions. 

Best Ad Sizes (Based on eCPM) - MobileDesktop: 

The same pattern repeats for desktop. Larger units have higher eCPM than the smaller ones, but 970×90 is an exception. Again, it accounts for ~ 1% of the total impressions. So, it’s safe to assume that the lack of demand is the reason for decreased eCPM. 

Best Ad Sizes (Based on eCPM) - DesktopWhat’s Next?

Have you overlooked any sizes? If so, leverage it now. As we are facing a crisis, it is better to focus on the units with higher demand and better eCPM and it includes — 300×250 and 320×50 for mobile and 728×90, 300×600, and 300×250 for desktop. 

Please note that our data is from the publishers we work with and so, we suggest you use it as a starting point. Over a period of time, you can pull granular reports from your Ad Manager account and make informed decisions. 

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