In short
- One impression = one ad render on one screen; the same person can generate many
- CPM prices impressions, CTR measures clicks per impression, frequency = impressions per person
- Impressions measure delivery, not attention; a half-scrolled ad still counts
- Impressions ÷ reach tells you how hard you are re-hitting the same audience
Why impressions matter
Every paid-social metric that matters is built on impressions: CPM is the price of a thousand of them, CTR is the share of them that got clicked, and frequency is how many of them the average person absorbed. If impressions are miscounted or misread, everything downstream inherits the error.
What an impression does not tell you
An impression is a delivery event, not an attention event. The ad rendered; nobody promises it was watched. That is why creative teams obsess over the first second of a video: the impression is bought either way, and the opening frame decides whether it becomes attention or scroll-past.
Impressions vs reach
Reach deduplicates impressions down to unique people. A campaign with high impressions and low reach is recycling its audience, which inflates frequency and invites ad fatigue. Comparing the two is the fastest health check on a prospecting campaign.
FAQ about Impressions
How are impressions counted?
Every time the ad renders on a screen, one impression is logged, whether or not anyone looks at it. The same person can generate dozens of impressions across days and placements.
What is the difference between impressions and reach?
Impressions are total views, reach is unique viewers. The ratio between them is frequency, and a rising frequency with flat reach means you are re-hitting the same audience.
Why do impressions matter if they do not measure attention?
Because they are the denominator of the metrics that do. CPM prices impressions, CTR is clicks per impression, and scroll-stop rate is 3-second views per impression. Bad impression data corrupts all three.