What Is Viewability? Viewable Impressions and Active View

What is viewability?

Viewability is a measure of whether a served ad actually had a chance to be seen. Under the Media Rating Council (MRC) standard, a display ad impression counts as viewable when at least 50% of its pixels are on screen, in an in-focus browser tab, for at least one continuous second. A video ad needs 50% of its pixels on screen while at least two continuous seconds play. Viewability rate is the share of measured impressions that met that bar.

An impression is counted when an ad is served and starts to render. It can still sit below the fold, in a background tab, or scroll past in half a second. Viewability separates those from impressions that were really on screen.

The viewable impression definition

The rules come from the MRC Viewable Ad Impression Measurement Guidelines (Version 1.0, June 30, 2014, prepared with the IAB). They are still the base for how the industry counts viewable impressions, checked on November 5, 2026.

The two tests run in order. The clock starts only once the pixel threshold is met, and short views do not add up: two half-second glimpses are not one viewable second.

Viewable does not mean seen. Google says in its Google Ads viewability help page that Active View “can tell you when ads are viewable, but it can’t guarantee that a user is looking at the screen at that time.”

What is Active View?

Active View is Google’s viewability measurement, reported in AdSense, Ad Manager and Google Ads. The Ad Manager overview of viewability and Active View applies the same thresholds: 50% of pixels for a continuous second for display, 30% for large ads, and 50% for a continuous two seconds for in-stream video. The main Active View metrics are:

• Measurable impressions: impressions that Active View was able to measure.
• Viewable impressions: measurable impressions that met the standard.
• Viewable rate: the share of measurable impressions that were viewable.
• Measurable rate: the share of all your impressions that Active View measured.

Read viewable rate together with measurable rate. A 70% viewable rate on 40% of impressions tells you less than it seems, because most of the traffic was not measured.

The formulas

Viewability rate = viewable impressions ÷ measurable impressions × 100

Viewable eCPM = earnings ÷ viewable impressions × 1,000

The second one shows what each 1,000 impressions that could actually be seen earned you. It is the number buyers who pay per viewable impression care about. For the basic CPM and eCPM math, see What is CPM? and eCPM vs RPM, or run your own numbers in the eCPM calculator.

How viewability affects eCPM

Advertisers can buy on viewability directly. Google Ads lets them bid with viewable CPM, which the vCPM help page says lets them “pay only for ad impressions measured as viewable.” An impression that never became viewable earns nothing from that buyer. Other buyers use viewability rate to decide which placements to bid on and how much.

Google’s AdSense viewability page says “publishers with the most viewable inventory will be in the best position to earn more revenue,” and that the most viewable ad position is “right above the fold, not at the top of the page.”

A worked example (illustrative)

All numbers are made up to show the math. A blog serves 200,000 display impressions a month and earns $400, an eCPM of $2.00.

• Viewable impressions: 90,000, so the viewability rate is 45% (assuming all impressions were measurable).
• Viewable eCPM: $400 ÷ 90,000 × 1,000 = $4.44.

The publisher removes a footer unit that almost nobody scrolls to, which served 60,000 impressions with 10% viewability and earned $40. The page now serves 140,000 impressions with 84,000 viewable, a 60% rate. Total earnings drop to $360 at first. If buyers then value the cleaner inventory more and bids rise by 15%, earnings climb to about $414, from fewer ads and a faster page. Whether bids rise that much depends on demand, so test changes over a few weeks. The ad revenue calculator helps you model the change, and How much does AdSense pay? covers what else moves RPM.

How to improve viewability

• Place ads where people pause: next to the content they came for, not at the very top or very bottom.
• Use responsive ad units so ads fit the screen instead of overflowing it.
• Lazy-load ads below the fold so an impression is only requested when the slot is close to view.
• Cut ads that are rarely seen. Fewer, better placements often beat many weak ones.
• Keep pages fast. An ad that loads after the reader scrolled past is not viewable.

Common mistakes

Why viewability does not apply to pay-per-result offers

Viewability is a measure for ads that are paid per impression. An offerwall is not. Advertisers pay when a user completes an offer and the conversion is confirmed by postback, so it does not matter how many pixels were on screen for how long. A wall opened for ten minutes with no completed offer earns nothing, and one completed offer earns the same whether the wall was viewable or not. The numbers that matter instead are conversion rate, EPC and earnings per active user, explained in eCPM and EPC explained and CPM vs CPC vs CPA.

Moonetix is a pay-per-result affiliate network, so its offerwall, Offers API and SDKs sit outside viewability entirely. If you run display ads and an offerwall side by side, judge each by its own model and compare them per 1,000 active users. Offerwall vs rewarded video compares those two formats.

Frequently asked questions