Advertising
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Impression
An impression is a single instance of an online ad being displayed to a user.
Detailed explanation
Impressions count how many times an ad is shown—not how many unique people saw it, and not how many clicked. They are the denominator for CTR and the basis for CPM buying.
Impression quality varies by viewability, placement, and frequency. High impression volume with weak CTR or CPA often points to creative or audience problems rather than “not enough reach.”
For “what is an impression” searches, this entry defines ad delivery. Read it with CPC, CPM, and CPA for the full cost-and-response picture.
Frequently asked questions
- What is an impression?
- An impression means a display of an online ad to a user—one showing of the creative.
- Why do impressions matter?
- Impressions measure reach delivery and underpin CTR and CPM, so they are essential for reading campaign scale and efficiency.
Related terms
Internal links for the topic cluster — read these concepts together.
- ReachReach is a core visibility metric that counts the number of unique users who saw a piece of content or an ad at least once within a given period.
- FrequencyFrequency is a performance metric that expresses how many times, on average, a single user has seen the same ad within a given time period.
- CPMCPM (Cost Per Mille) is the cost of 1,000 ad impressions; it is one of the most common media buying units.
- CTRCTR (Click-Through Rate) is the percentage of impressions that result in a click on an ad or link.