In online advertising, an impression is an instance of an ad being seen. For example, if you use Google AdWords to purchase the keyword “organic chocolate” and user searches prompt your ad to appear 143 times, you would say your ad has had 143 impressions. Impressions are usually tracked alongside click-through rates (CTRs), but your ad does not need to be clicked to be recorded as an impression.
In addition to cost-per-click advertising, cost-per-impression (CPI) is common today. As demonstrated in our example above, your ads are typically viewed when you sign up for a campaign and select relevant keywords, which prompt your ad to appear. Although malicious practices from bots can alter your impression count, many services are now in place among popular web browsers to prevent and intervene with such activity.
The current method of counting impressions is under debate with a revision being evaluated. The new method separates impressions into two categories: served impressions and viewable impressions. This distinction would allow online marketers to determine if an ad was simply recorded by a server (but not necessarily viewable before a user clicked away) or if an ad was 50 percent viewable (or above) for one second or more.
With each ad campaign, you want to track your impressions and your click-through rate. If your ads are appearing frequently, but rarely being clicked, you need to revisit your digital media strategy for a more successful approach.