How it works
The ad network reports impressions to the measurement platform, either through an impression tracking link fired when the ad is shown or through its own self-attributing integration. At first open the platform checks clicks first. If none qualifies, it looks for an impression inside the view-through window, which is short, commonly 24 hours or less. Apple's SKAdNetwork also supports view-through attribution, with a 24-hour window set by Apple.
Why it matters for an app team
Video and display ads often persuade without being clicked. Without view-through measurement these formats look weak next to search or rewarded ads, and budget drifts towards whatever collects the last click.
In practice
Example with made-up numbers: a video campaign records 200 click-through installs in a week. With a 24-hour view-through window switched on, another 80 installs are credited to it that had been counted as organic.
Common confusion
A view-through install is weaker evidence than a click-through one, because an impression is easy to serve and hard to verify. Some advertisers report the two separately or pay a lower rate for view-through installs. Whether the ad was really visible on screen depends on each network's own definition of an impression.