Viewable CPM (vCPM) is a way of paying for ads in which you are charged per 1,000 viewable impressions, rather than per 1,000 times the ad loads. An impression only counts as viewable if enough of the ad appears on screen for long enough that someone could actually have seen it.
How viewable CPM works
Google measures viewability with a technology called Active View. Under the industry standard Google follows, a display ad counts as viewable when at least half of it is on screen for at least one continuous second. For video, half the player must be on screen for at least two continuous seconds while the video plays. An ad that loads at the bottom of a long article and is never scrolled to is an impression, but not a viewable one.
With vCPM bidding you set the most you will pay for 1,000 viewable impressions and are charged only for those. The reporting sum is simple: cost divided by viewable impressions, multiplied by 1,000. If you spend £60 and receive 20,000 viewable impressions, your vCPM is £3.
At the time of writing (October 2026), manual vCPM bidding is offered mainly in Display campaigns set up for awareness, while video reach campaigns use target CPM and most other campaign types rely on automated bidding. The options you see depend on the goal you choose, so check what your account offers before planning around it.
Why it matters
A standard CPM charges for every load, including ads below the fold, in background tabs or squeezed into slots nobody looks at. On display inventory those unseen impressions can make up a large share of the total. Paying on a viewable basis moves that risk away from you: the price per thousand looks higher, but you are paying for impressions that had a chance to work.
For a UK business running a small awareness campaign, such as an independent cinema reopening in Leeds, the difference is real. The budget is limited, and every pound spent on an ad nobody could see is a pound not spent reaching people within travelling distance.
Viewability is a minimum, not a measure of attention. Being on screen for one second does not mean anyone noticed the ad, and it says nothing about whether the site was a sensible place for your brand to appear.
Common mistakes
- Comparing a vCPM directly with a CPM and deciding vCPM is dearer. Compare the cost per viewable impression on both, using the Active View columns.
- Using vCPM for a campaign whose job is enquiries or sales. It aims for being seen, not for clicks or conversions.
- Assuming viewable means suitable. Ads can sit fully on screen inside low-quality apps and made-for-advertising sites, so review placements and add placement exclusions.
- Ignoring the measurable rate. If Active View cannot measure a large share of impressions, the viewability figures describe only part of the campaign.
- Reading a high viewable rate as success without checking reach, frequency or any later effect on brand searches.
How to act on it
Start by deciding whether the campaign is about being seen or about getting a response. If it is about being seen, vCPM is a fair way to pay for display inventory. Add viewable impressions, measurable impressions and viewable rate to your reports, and work out the effective cost per thousand viewable impressions for any CPM campaigns running alongside, so the comparison is like for like.
Then check where the viewable impressions came from. A high viewable rate on a handful of mobile games is worse value than a lower rate on sites your customers actually read. Exclude poor placements weekly for the first month, set a frequency cap, and judge the campaign on unique reach and any lift in brand searches. Choosing the right bid type for awareness campaigns is part of my Google Ads management work.