Better Monetisation with Header Bidding

Increase ad revenue by simultaneously collecting multiple bids from a variety of demand sources each time a new impression is available


Everything You Need to Know About Ad Viewability

We are just beginning to scratch the surface of viewability as a defined parameter instead of a theory. Read to know all about Ad Viewability

“The ad is served.”

“Did the user get to see it?”


That’s the question viewability answers. It sounds so obvious in hindsight—that for someone to interact with an ad impression—it must first be visible. But the ad tech industry is only now beginning to scratch the surface of viewability as a defined parameter instead of a theoretical concept.

“Viewability has been in-market for more than a year (since before 2015) as a transactional metric – and as a planning metric for some time as well.” — Sherrill Mane, former SVP, Research, Analytics, and Measurement, IAB

Advertisers are already bidding and willing to pay through their nose for vCPM (Cost-per-thousand viewable) impressions—which is perfect because they get to pay for only those impressions that their intended audience have seen.

With Active View, Google created a framework for publishers to get viewability measurement data and use it to understand and improve the value of their ad inventory.

What is Viewability?

AKA: When is your ad impression considered viewable?

In Active View terms, “An impression is considered a viewable impression when it has appeared within a user’s browser and had the opportunity to be seen.”

More specifically, per IAB (Interactive Advertising Bureau) viewability criteria, the display ad must have:

  • At least 50% of its pixels visible in the user’s browser window—for minimum 1 second.
  • At least 30% of its pixels visible in the browser window (if it has more than 242K pix – large ads, for instance)—for minimum 1 second.
  • In-stream video ads must have at least 50% pixels visible for 2 seconds to be considered ‘viewable’.

This criterion is commonly called MRC Standard. Seems simple enough, yeah? But there’s a little catch, and it will trip you up if you’re not careful.

Measuring Viewable Impressions

There’s a lot of confusion when it comes to counting the number of viewable impressions you have in your inventory. Let me clear it up once and for all.

The one solid rule that applies to viewability, i.e., you can’t count what you haven’t measured.

This means that for you to actually start getting viewable impressions (and make revenue off of them), you need to first make your impressions measurement-ready. If you’re a GA-junkie, compare this to manually enabling certain reporting features in Google Analytics (example: Interests report).

Your ad impression should be Eligible (Active View enabled) and Measurable (data reporting is available for that ad unit/impression) before it becomes viewable by Active View based on the aforementioned IAB criteria.

A Venn diagram that explains Viewable Impressions.

As of now, Google is still working its way through incorporating Active View measurement and reporting metrics on all its ad products. Active View currently measures viewable impressions from AdSense for Content, AdSense for Video, and AdSense for Games units only.

Ads served through Google Publisher Tags and/or Mobile Ads SDK also work (Active View is already enabled).

When is an Ad Impression Not Viewable?

Even with Active View enabled with all pixels rendered and visible on the viewport for hours, your ad impression may not be accounted for when the tag comes a-knockin’ to capture viewability data. This happens in AdSense ad impressions when:

  • Ad tag is placed in a cross-domain iframe
  • A backup image or default ad is served
  • You are still using old AdSense codes. In which case… why?

Keep in mind that Active View in AdSense is still in beta stage (and working its way up).

Why Should You Care About Viewability?

Google has tested and evaluated the impact of viewability for marketers since as far back as 2015. Advertisers involved in the study found that:

  • Viewable ads saw as much as 50% improvement in conversion rates
  • Viewable ads increased brand lift (customer awareness and interaction that can be attributed to an advertising campaign) by 10.3%

“The business impact of buying (ad impressions) based on MRC standard is real. Marketers are not saying that they want a ‘percentage of their campaign’ to be seen; rather, they are saying they want to pay only for viewable impressions.” — Neal Mohan, VP of display and video advertising products, Google

So when the long-term value of your ad inventory is increasingly measured entirely in terms of viewability, it becomes a no-brainer for publishers to work on enhancing it. Yet, according to Google, publisher viewability averages at 50.2%. So if viewability became a standard metric today; you, as a publisher, would likely end up losing half your ad revenue in one fell swoop.

The following section discusses how to enhance viewability to increase the long-term value of your inventory.

Improving Ad Viewability

According to a highly commended Primer on Ad Viewability (published earlier this year by IAB), there are 4 ‘primary levers’ that affect ad viewability: site content, site design, ad latency, and ad tech strategy.

If you have engaging content (always a plus), a clean (read: easily-navigable) site design and page layouts, quick-rendering ads, and a smart ad optimization tool in place—congratulations! You are already well on your way to improved viewability. Skip this section and do what you please.

For the rest of us who make up the disgruntled, dissatisfied mob, here are some viewability best practices to adhere to:


Note: While it ranges across content verticals and industries, content that holds a user’s attention has the highest viewability. Drop everything else and start with creating awesome content first so users would actually spend time reading it (instead of skimming over or simply bouncing away).

Reducing Ad Latency

Latency is like slow page loading times but for ad units.

“Ad latency is the perceivable amount of time before an ad makes an appearance in its intended frame.”

It’s been known to be caused by server redirects.

So when an ad is delayed, it’s spending more time hauling itself from ad server/CDN to your front-end than on display. MRC standard (and Active View) only takes time duration of visibility into account. By the time it’s fully rendered, the user has moved away from that section and you lost a viewable ad impression.

Reduce this lag by:

  • Reducing passbacks while using GPTs.
  • Implementing Asynchronous ad calling (loading ads in parallel with page content). In AdSense, the default code type is set to ‘asynchronous’. For best results with the code, Google recommends that you set all ad units to asynchronous (or otherwise) on a given page.
  • Implementing Smart Loading (aka lazy load) for ad units. Keep in mind that this is a fail-safe method—if the ad loads too slow (typical for a large ad) and the user scrolls down too fast, your ad will likely not be viewable. Also, hiding previously rendered ad slots once a user has scrolled down may still not be the best thing—the user could rapidly scroll up at any time.

In case of 3rd party vendors, whet them thoroughly for ad latency (against your site’s baseline TTFB or avg. page load time). AdSense, for instance, has a certification process for 3rd party vendors that includes privacy, latency, creatives policy compliance, and more.

Improving Ad Layouts and Placement

First things first, find your page fold (for a given screen resolution) using Google Analytics. Go to Audience >> Technology >> Browser and OS, and select Screen Resolution as the primary dimension. Test new placements on low-risk (low session counts) resolutions first for a device type.

Now, here’s what the statistics have spoken about most viewable ad placements:

  • Horizontal ads (728×90, 300×250, 160×600, 468×60, and 320×50) have shown high viewability when placed right above the fold i.e., at the bottom of ‘the first, immediately visible screen’; not at the top of the page.
  • Vertical ads have the highest viewability rates. Visitors spend time reading an interesting bit of content thoroughly from top to bottom of the screen, enhancing viewability for the ads placed vertically along it.

Note that just because Above-the-fold (ATF) works great does not mean that ads below the fold will never be seen. Good content that motivates users to scroll to the bottom will make ads below-the-fold viewable as well.

For the love of everything: Do not overload any area on your page (especially ATF) with ads. Too much of a good thing (for you) may act as visitor-repellant (bad UX: clutter + slow load time).

Google’s viewability best practices also stress the importance of testing and reiterating the site design and ad placements for most viewability, because user behavior varies and your particular website isn’t like everybody else’s. What works for most may not work for you after all.

What’s Next?

As advertisers and publishers continue to strive for viewability, the metric itself will evolve and incorporate more ways of measuring an ad’s effectiveness—on different devices (mobiles, tablets, wearable tech) and formats (audibility time for videos).

There may also be a shift in cards—ads will still hold CTR in regard (that’s the one awesome thing about internet: direct, instantaneous interaction), but their most common purpose (and success criteria) could change from conversion to brand awareness.


1. What do we mean by viewability?

 In digital advertising, viewability refers to the number of impressions that have been seen. It only reports impressions that can be viewed.

2. Why is viewability important?

Money is wasted on ads that aren’t seen. In addition to providing agencies and brands with a better understanding of a campaign’s effectiveness, measuring viewability helps them allocate their advertising dollars.

3. How do you measure viewability?

Divide the number of viewable ads by the number of measured ads to calculate the viewability rate.