Glossary
Impression
One instance of an ad being served, regardless of whether it was seen or clicked.
Media BuyingFoundationAlso called: Ad ImpressionSource: MRC
Definition
One instance of an ad being served, regardless of whether it was seen or clicked.
Why it matters
Impressions are the base unit almost every other metric (CPM, CTR, viewability rate) is calculated from.
Key consideration
A served impression is not the same as a viewed impression — always check whether a reported impression count is gross-served or viewable before comparing across sources.
Related terms
Practitioner notes
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