Measurement

Ad Impression — Definition & Explanation

A single instance of an ad being displayed to a user. Impressions are the fundamental unit of measurement in digital advertising and are used to calculate CPM (cost per mille/thousand impressions).

How Ad Impression Works

An impression is counted when the ad server returns ad code to the browser and the code fires a tracking pixel or beacon. Different measurement vendors define impression counting differently; MRC accreditation sets the standard for consistency.

Why Ad Impression Matters for Publishers

Impression count forms the denominator for every key publisher metric — eCPM, fill rate, viewability, and revenue. Maximizing filled, viewable impressions is the foundation of publisher monetization strategy.

Frequently Asked Questions

What is the difference between a served and a viewable impression?

A served impression means the ad code loaded. A viewable impression means the ad met MRC standards: 50% in-view for 1+ second. Advertisers increasingly pay only for viewable impressions.

How can publishers increase impression volume?

By improving page load speed, reducing bounce rates, increasing pages-per-session, and ensuring ad placements load reliably across devices.

Does Stellor Media count impressions independently?

Stellor Media passes impression data to publisher dashboards and reconciles with third-party measurement for accuracy.

Related Terms

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