Viewable impression goals in Google Ad Manager: a guide for publishers

By default, goal-based line items in Google Ad Manager aim to deliver a certain number of impressions. But it is possible to set a goal based on viewable impressions instead (as well as clicks, but let's not worry about that today):

Viewable impressions option

What are viewable impressions, and what as a publisher do you have to consider when setting a goal based on them?

Viewability and viewable impressions

Google Ad Manager (and indeed other Google properties such as Google Display Network and YouTube) adhere to the standard industry definition of viewability. As Google explains:

In an effort to foster greater standardization around what is considered a viewable impression, the Interactive Advertising Bureau (IAB) and the MRC [Media Rating Council] collaborated with hundreds of major agencies, advertisers, publishers, and technology providers (including Google) to develop a collective industry standard.

At Google, we support the IAB and MRC definition of viewability: a minimum of 50% of the ad is in view for a minimum of one second for display ads or two seconds for video ads.

Strictly speaking, that 50% is based on pixel count - a standard skyscraper is 120x600px, or 72,000 pixels in total, so 36,000 of those pixels would need to be visible for one second or more. Very large display ads of at least 242,500 pixels only need to have 30% of their pixels in view for at least 1 second to be considered 'viewable'.

The second part of that definition, "in view", means "visible in the browser window". In other words, an ad impression served lower down on the page, outside the viewport, wouldn't be considered viewable until the user scrolled down far enough to see it. I guess the terminology is 'viewable' rather than 'viewed' because even if an ad is in the viewport, you can't force someone to look at it - or prove that they have done so!

Anywa, Google has a very handy 'viewability in action' demo which demonstrates how viewability works in real time:

Taking this further, it is understandable why savvy advertisers would want their campaign to have a goal based on viewable impressions rather than just impressions. After all, what's the point of paying for ad impressions that nobody sees?

What viewability means for publishers

But setting a goal in viewable impressions does not somehow magically force Google Ad Manager to only serve viewable impressions. It will continue to serve the same old mix of viewable and non-viewable impressions to your line item, the only difference being that the non-viewable ones now won't count towards the goal. So if your site has low viewability, it is possible to burn through a lot of impressions in order to hit the goal. And those are impressions that could otherwise have been used to deliver on other campaigns.

You can see this in action in Google Ad Manager by looking at any order with a line item that has a viewable impression goal. It will show you both the number of impressions served and the number of viewable impressions served. The latter will invariably be lower:

Viewable impressions in GAM

Strangely, if your line item has an impression goal rather than a viewable impression goal, Google Ad Manager will not show you the number of viewable impressions at all - it just says N/A instead:

Viewable impressions N/A

Whether this is to avoid confusion or for some technical reason I do not know. If you need to find out the number of viewable impressions for such a line item, then you will need to generate a report.

Speaking of reports, it is possible to creating a simple report in Google Ad Manager that gives you a feel for your site's viewability:

Creating a simple viewability report

  1. Log in to Google Ad Manager
  2. Go to Reporting > Reports
  3. Click New Report
  4. Give your report a Name
  5. Select a date range, eg Dynamic 'Last 30 days'
  6. Under Dimensions, search for and tick Ad unit (all levels)
  7. Under Metrics, search for and tick Total Active View % viewable impressions
  8. Click SAVE AND RUN

The report you have just generated will list all of your ad units and, for each one, the percentage of measurable impressions served to them that were viewable. The higher the percentage, the better. Here's a very simple example with just the one ad unit:

GAM viewability report

When you were selecting the metric 'Total Active View % viewable impressions', you may have noticed the very similar-sounding 'Ad server Active View % viewable impressions' and wondered what the difference is. Simply put, the latter does NOT include impressions from AdSense and Ad Exchange.

It also raises the question, what on earth is Active View? Here's Google's definition:

Active View is Google's viewable impression measurement technology. It's our solution for measuring and buying viewable impressions across the web and is accredited by the Media Ratings Council. It measures in real-time, on an impression-by-impression basis, whether or not an ad was viewable to a user. It's effortless, free and integrated into all of our advertising platforms and Active View metrics are fully transparent, based on the direct measurement of each impression, not sampling or extrapolating.

Viewability, deliverability and CPM

Going back to your viewability report - you can use this to get a feel for how a viewable impressions goal might impact either the number of impressions that need to be delivered, or the CPM of a campaign, or both.

For example, if an advertiser offers you £1,000 for delivering 100,000 impressions, that equates to a CPM (cost per thousand impressions) of £10:

Cost to advertiser£1,000
CPM£1,000 /  (100,000 / 1,000) = £10

But if the advertiser wants 100,000 viewable impressions and you have a viewability of 50%, you would need to deliver 200,000 impressions (100,000 % 0.5) in total to hit that goal. That reduces the CPM to just £5. Incidentally that figure of £5 is your 'viewable CPM' or vCPM. And suddenly you have a financial incentive to improve your website's ad viewability!

Viewable impressions100,000
Cost to advertiser£1,000
vCPM£1,000 / (100,000 / 1,000) * 0.50% = £5

Other considerations

And I just wanted to finish by mentioning another couple of 'gotchas' that might catch you out with viewable impression goals:

Once a line item has started Delivering, it is not possible to swap from an 'impressions' goal to a 'viewable impressions' goal or vice versa (or indeed from a CPM to a Viewable CPM or vice versa). The option is greyed out and cannot be changed.

Combining a 'viewable impressions' goal with a per-user frequency cap can make it significantly more difficult to hit target. Although the frequency cap does not 'burn through' impressions in the same way that a viewable impressions goal might, it does reduce the number of impressions that are elible for that line item. If you are going to go down this route, make sure you run a forecast - even if you are sure in yourself that you have enough impressions to deliver!

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James Clark
Hi! I'm James Clark and this is my website. I publish all my guides completely free, so if you find them useful then please:
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