An impression is a single instance of a digital advertisement being displayed on a webpage, in an application, or on a social media feed.
In digital advertising, an impression, sometimes called an ad view, is counted each time an ad is fetched from its source and is displayed on a user's screen. It is one of the most fundamental metrics for measuring the delivery of an ad campaign. An impression does not guarantee that the ad was actually seen by the user, only that it was served and rendered on the page. To address this potential discrepancy, industry standards have evolved to distinguish between different types of impressions. A 'served impression' is counted when an ad server sends an ad to a publisher's website. A 'viewable impression' is a more stringent metric, typically counted only when a certain percentage of the ad's pixels (e.g., 50%) is visible on the user's screen for a minimum duration (e.g., one second). This distinction is critical for evaluating the true exposure of an ad. Impressions are the foundational unit for many advertising pricing models, most notably Cost Per Mille (CPM), where 'mille' means one thousand. In a CPM model, advertisers pay a set price for every 1,000 impressions their ad receives. This model is commonly used for campaigns focused on brand awareness and reach.
Impressions are the starting point for nearly all digital advertising analytics. They provide the basic measure of an ad campaign's size and reach, indicating how many times an ad has been put in front of a potential audience. By tracking impressions, advertisers can manage budget pacing, ensure their campaigns are delivering as planned, and calculate other essential performance metrics. Metrics like Click-Through Rate (CTR) and Conversion Rate are derived from impressions (Clicks ÷ Impressions = CTR). Without an accurate count of impressions, it is impossible to understand the relative performance of an ad creative or the efficiency of a campaign. For brand awareness objectives, the sheer volume of impressions is a key indicator of success, aiming to maximize exposure to the target audience.
