Glossary · MeasurementTOFU
Viewability
The short answer
Viewability measures whether an ad impression had a genuine chance to be seen. The widely used industry standard counts a display impression as viewable when at least 50% of the ad's pixels are on screen for at least one continuous second, and a video impression when 50% is visible for two seconds.
An ad served at the bottom of a page nobody scrolled to is still counted as an impression — but it was never viewable.
Why it matters
In programmatic and display, a meaningful share of impressions can be non-viewable. Paying for them is paying for nothing. Buying on viewable CPM (vCPM), setting viewability floors, or using verification tools protects the budget.
How to improve viewability
- Buy from curated publisher inclusion lists
- Prefer above-the-fold and in-content placements
- Use verification partners on meaningful spend
- Exclude placements with consistently poor viewability
- Consider attention metrics, which go beyond basic viewability
Improving viewability
- Buy viewable impressions where platforms allow
- Prefer above-the-fold and in-content placements
- Use verification tools in programmatic buying
- Exclude low-viewability sites and apps
- Avoid oversized or slow-loading creatives
Viewability in practice
A display campaign finds only half its impressions were viewable. Moving budget to placements with higher viewability improves real reach.
Common mistakes
- Buying impressions without viewability data
- Ignoring below-the-fold placements
- Paying for non-human traffic
Frequently asked questions
Is a viewable impression the same as a seen impression?
No — viewability means the ad could have been seen, not that anyone looked at it.
Does viewability apply to Meta and YouTube?
Those platforms have their own measurement, but the concept matters most for open-web display and programmatic.
Does viewability guarantee attention?
No — viewable doesn't mean noticed. Attention metrics and outcomes matter too.
Is viewability relevant on Meta and YouTube?
Platform-native placements are generally viewable by design; viewability matters most for open-web display and video.
What is a viewable impression?
Under common standards, at least half the ad is visible for at least one second for display, or two seconds for video.
How can viewability be improved?
Choose better placements, formats and verified inventory.
Related terms
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