It’s important to understand that:
- an impression measures the delivery of an ad,
- whereas viewable impressions measure whether a user has seen an ad.
An impression is viewable depending of the viewability measure
To be viewable, an impression must meet a specific set of criteria defined by the Interactive Advertising Bureau (IAB).
- For display ads, 50% of the ad’s pixels must be visible in the browser window for one continuous second.
- For larger display ads (those greater than 242,000 pixels), 30% of the ad’s pixels must be visible in the browser window.
- For in-stream video ads, 50% of the ad’s pixels must be visible in the browser window for two continuous seconds.
These are the Google criteria that must be met before an ad impression is counted as viewable.
- A user must navigate to an area of the page where 50% of the ad’s pixels are visible in the browser window.
- The user must pause or proceed slowly enough that the ad is on screen for 1 continuous second. Scrolling past an ad too quickly does not count.
- The ad must be rendered when the user navigates to it.