Impression

Also known as: ad view

An impression is counted every time a creative (ad) is served to a user. It is one of the foundational performance indicators used to measure campaign delivery and reach.

Impressions are counted and reported by ad servers, which use tracking tags (pixels) to record each instance. Notably, if a user refreshes the page and sees the same ad again, a new impression is counted — each served instance is tracked independently.

In pricing models, impressions are grouped into units of 1,000, expressed as CPM (cost per mille), where mille is Latin for one thousand. CPM is the standard unit because the price per individual impression is too small to be practical as a standalone figure — a single impression might be valued at $0.002, making per-impression billing unwieldy. Grouping into thousands produces a more workable number for transacting and reporting.