What is Impressions?

An impression is counted each time your ad or listing is shown to someone, whether or not they interact with it. Impressions measure reach and visibility — how many times you appeared — but not effectiveness, since a shown ad that nobody clicks still counts. They're most useful as a denominator: click-through rate is clicks divided by impressions, and a high impression count with a low CTR usually means your targeting is too broad or your message isn't landing. Judge campaigns by conversions, not impressions alone.