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What is viewability and why does it matter?

Viewability measures whether an ad was actually visible to a user — not just loaded somewhere on a page no one scrolled to, or sitting in a background browser tab. It has become one of the most important quality signals in programmatic advertising, and it has a direct effect on the prices buyers are willing to pay for your inventory.

The industry standard​

The current viewability standard, established by the IAB and MRC and adopted by most major buyers and verification platforms, defines:

  • Display ads: at least 50% of the ad must be visible on screen for a minimum of one continuous second
  • Video ads: at least 50% of the player must be visible on screen for a minimum of two continuous seconds

An impression that does not meet this threshold is technically served but is not counted as viewable. Buyers increasingly filter campaigns to exclude low-viewability inventory, or pay substantially less for it.

Why viewability affects your eCPM​

Advertisers pay for outcomes, and an ad that is never seen cannot deliver any outcome. Premium campaigns from brand advertisers — which tend to pay the highest CPMs — almost universally require strong viewability. If your viewability is low, those buyers will either exclude your inventory or bid far less for it, reducing auction competition and pushing down eCPM.

Improving viewability is one of the most reliable levers for improving eCPM — it does not require more traffic, more ad products, or any changes to your demand setup.

What counts as a good viewability rate?​

Based on industry benchmarks from the IAB and major verification platforms, a good viewability rate for display ads typically falls between 60% and 70%, with premium publishers often exceeding 70%. For video, 70–80% is generally considered strong, depending on placement and format.

Common causes of low viewability​

  • Ad units placed far down the page, below where most users stop scrolling — particularly on mobile
  • Ads loading in iframes that measurement technology cannot correctly detect as visible
  • Fast-scrolling pages where users move past ad positions before the creative has fully loaded
  • Heavy ad creatives that load slowly, especially on mobile connections

Reading viewability in the dashboard​

The Storyteller card shows viewability as a percentage for Storyteller placements specifically. In the Reports section, Viewable Impressions is a raw number — to calculate the rate, divide Viewable Impressions by total Impressions and multiply by 100.

Example

You have 800,000 total impressions and 560,000 viewable impressions. Viewability rate = 560,000 ÷ 800,000 × 100 = 70%.

Practical tips
  • If your viewability is below 50%, auditing where your ad units sit on the page — particularly on mobile — is the highest-priority action. Moving a below-the-fold unit to a mid-content position can produce an immediate improvement.
  • Viewability and eCPM tend to move together over time. Improving viewability is one of the most effective ways to improve eCPM without needing additional traffic.

See also: Understanding eCPM · Video completion metrics explained