Viewability

Viewability is a measurement standard that determines whether a digital ad had the opportunity to be seen by a user. According to the IAB/MRC standard, a display ad is considered viewable if at least 50% of its pixels are visible in the browser viewport for at least one continuous second. For video ads, at least 50% of pixels must be visible for at least two continuous seconds.

Key Takeaways

• Measures whether an ad was actually visible on screen, not just served
• IAB/MRC standard: 50% of pixels visible for 1 second (display) or 2 seconds (video)
• Google reports viewability through Active View metrics in Google Ads
• Average viewability across the web is approximately 50-70% depending on placement
• Non-viewable impressions represent wasted spend on CPM campaigns

What Is Viewability

Viewability addresses a fundamental gap in impression counting: an ad can be “served” (loaded by the browser) without ever being “viewed” (visible on the user’s screen). This happens when ads load below the fold, in background tabs, or in areas the user never scrolls to.

Scenario	Served	Viewable	Explanation
Ad loads above the fold, user sees it	Yes	Yes	Standard viewable impression
Ad loads below the fold, user never scrolls down	Yes	No	Served but never visible
Ad in a background browser tab	Yes	No	Tab was never active
Ad loads but user scrolls past in <1 second	Yes	No	Visible time threshold not met
Ad in an iframe that is too small to display	Yes	No	Pixel threshold not met

How It Works

Google measures viewability through Active View, its MRC-accredited viewability measurement technology:

1. Ad serving — The ad is loaded on the publisher’s page
2. Pixel detection — Active View monitors how much of the ad is within the browser viewport
3. Time tracking — The system measures how long the ad remains in the viewable area
4. Classification — If the IAB/MRC thresholds are met, the impression is classified as “viewable”

Google Ads reports viewability through these metrics:

Metric	Definition
Viewable impressions	Impressions that met the viewability standard
Viewable rate	Percentage of total impressions that were viewable
Active View measurable	Impressions where viewability could be measured
Active View not measurable	Impressions where measurement was not possible

These metrics are available for Display and Video campaigns in the Google Ads interface under Columns > Viewability.

Viewability varies by ad position and format:

Position/Format	Typical Viewability Rate
Above the fold	68-80%
Below the fold	30-45%
Leaderboard (728x90)	55-65%
Medium rectangle (300x250)	50-60%
Skyscraper (160x600)	45-55%
Video (in-stream)	70-85%

Practical Example

A brand awareness campaign runs on the Google Display Network with CPM bidding:

Metric	Value
Total impressions served	1,000,000
Viewable impressions	620,000
Viewable rate	62%
CPM bid	$5.00
Total cost	$5,000
Effective cost per viewable impression	$8.06 per 1,000

Analysis: The advertiser paid $5.00 CPM for served impressions, but the effective cost for viewable impressions is $8.06 CPM — 61% higher. 380,000 impressions (38%) were served but never actually seen by users.

If the advertiser switches to viewable CPM (vCPM) bidding:

• Bid: $7.00 vCPM (only paying for viewable impressions)
• 620,000 viewable impressions at $7.00 vCPM = $4,340
• Savings: $660 compared to standard CPM, with guaranteed viewability

Why It Matters

Viewability is a critical quality metric for any brand awareness or CPM-based campaign. Paying for impressions that are never seen is the advertising equivalent of printing a billboard facing a wall. Google’s vCPM bidding option and Active View reporting give advertisers the tools to measure and pay only for viewable impressions. For performance-focused CPC campaigns, viewability is less directly relevant since you only pay for clicks, but low viewability still reduces the total pool of users who have the opportunity to click. Monitoring viewability rates helps identify low-quality placements and informs brand safety decisions about which sites and positions to target or exclude.