Boardroom Definition

Viewability is a verification metric that tracks whether an ad impression meets the minimum industry standards for visibility. According to the Media Rating Council (MRC), a display ad is considered "viewable" if at least 50% of its pixels are in view on the user's screen for a minimum of one continuous second. For video, the standard is 50% of pixels for two continuous seconds. It filters out impressions that load in the background, at the bottom of a page, or on a tab the user never visited.

Advanced Math and Science Application

Viewability is calculated as a percentage of measured impressions, not necessarily total impressions (as some environments cannot be measured).

  • Formula: (Viewable Impressions / Total Measured Impressions) x 100.
  • The Financial Impact (vCPM): To understand the true cost of media, buyers calculate the "Viewable CPM" (vCPM).
    • Formula: CPM / (Viewability Rate / 100).
    • Example: If you buy a $5.00 CPM with 50% viewability, your effective cost for a viewable impression is actually **$10.00 vCPM**.

The Real Scoop

Viewability is the "floor," not the "ceiling." In 2026, it is merely a baseline requirement for transaction, not a proxy for human attention. A common misconception is that 100% viewability is the goal.

Ironically, inventory with 100% viewability often performs poorly. This is because the most viewable ad units are often "Sticky Footers" or "Interstitials" that lock onto the screen and annoy users, leading to "banner blindness." Conversely, high-quality editorial content often has lower viewability (60-70%) because users scroll quickly to read the article. Savvy buyers accept a blend of viewability to ensure they are accessing premium reading environments, rather than just optimizing for technical metrics.

Watch Outs

  • The "Measured" Trap: A report might show "90% Viewability," but check the "Measurability Rate." If the vendor could only measure 10% of the campaign, that 90% stat is statistically insignificant.
  • Mobile Discrepancies: Mobile web viewability behaves differently than In-App. On mobile web, ads often load after the user has scrolled past the slot due to slow load times, crushing viewability scores.
  • Overselling: Specialized B2B video or premium CTV often commands a higher premium because the viewability is inherently higher (non-skippable), whereas standard display is often considered "High Premium" if priced similarly without the viewability guarantees.

External Resources