Quick answer
Viewability is whether an ad was on screen: at least half of it visible for at least one second. It separates impressions that reached a screen from ones served off it, and says nothing about whether anyone looked.
Viewability
DefinitionAn impression is counted when an ad is served, including below the fold and in tabs no one is looking at. The viewability standard (half the ad, one second, two seconds for video) was introduced so buyers could stop paying for ads that never reached a screen. Most platforms now report viewable impressions alongside served ones.
Also called: Viewable impressions, Attention metrics.
How is viewability measured?
A verification script on the page checks whether the ad's pixels are within the browser viewport and for how long. The standard most buyers use: at least half of a display ad in view for one continuous second, half of a video ad for two seconds. Impressions that meet it are "viewable"; the share that do is the viewable rate. Platforms report it themselves or through third-party verification vendors.
Ads below the fold, in background tabs, in collapsed sections or in windows the reader minimised are served but not viewable. On many pages that is most of them, which is why the standard exists.
Why is viewable not the same as seen?
Because the standard measures the screen, not the eyes. Eye-tracking and attention studies find that 35% of "viewable" ads are actually looked at (Lumen / Adelaide attention research): a banner can be fully on screen while the reader looks at the article beside it, and developers have spent years learning to look past anything banner-shaped. Viewability removes the impressions that never had a chance; it says nothing about the ones that had a chance and were ignored.
Common mistakes
- Treating a high viewable rate as proof of attention.
- Buying on served impressions when viewable ones are available.
- Comparing viewable rates across formats that are read differently.
- Reporting viewability to a team that should be hearing reads and follows.
How developers experience it
- A banner on screen is still a banner they learned to ignore.
- A card in the feed is read because it is in the reading path.
- They never think about viewability; they think about whether the post was worth it.
How should a developer campaign use viewability?
As a floor. Ask any platform for its viewable rate and treat a low one as a disqualifier. Then judge the campaign on measures that imply attention: reads to the end, upvotes and comments, follows on the company page, clicks, and conversions with a weeks-long window. A native card in a feed is viewable the way the posts around it are viewable; what matters is that it is read the way they are read.
When comparing channels, put viewable rate, engagement and cost per activated developer side by side. A display network with a high viewable rate and no engagement is delivering ads to screens nobody is looking at.
What should you ask a platform about viewability?
- What is the viewable rate, and who measures it?
- Is it reported per placement, so you can see which ones reach a screen?
- Do you bill on served or viewable impressions?
- What do you report beyond viewability: reads, engagement, conversions?
A platform that only reports viewability is telling you the ad reached a screen. A platform that reports reads is telling you it reached a person.
On daily.dev
How it works on daily.dev
daily.dev reports what viewability cannot: reads, upvotes, follows and the conversions your conversion pixel records, because In-Feed Ads are read like the posts around them rather than measured for being on screen.
Explore my optionsServed, viewable, seen
| Capability | Served impression | Viewable impression | Seen |
|---|---|---|---|
| Means | The ad was delivered to the page | Half of it was on screen for a second | Someone looked at it |
| Counted by | The ad server | Verification vendors | Attention and eye-tracking research |
| Proves | Delivery | Opportunity to see | Attention |
| For developer campaigns | A floor, not a result | Necessary, not sufficient | What reads, follows and conversions stand in for |