Impression

Saying how far an ad spread requires settling what gets counted first. If one person saw the same ad three times, counting that as 1 or as 3 changes the number in the report by a factor of three.

The problem surfaced in Pagedeck's first ad report. Ravi wrote impressions: 240,000, and Grace asked whether that meant 240,000 people. It didn't. Eighty thousand people saw the ad an average of three times each. Read as one number, the ad looks like it spread three times as far as it did.

So this value gets used with the point pinned down that it counts occurrences, not people. People get counted separately, and how many times each person saw it gets counted separately too, with its own name.

Add up every time the ad appeared on a screen. One person seeing it three times counts as 3.

The relationship to people is a multiplication: impressions equal the number of people who saw the ad times the average number of times each saw it. Eighty thousand people at three times each is 240,000. Knowing two of the three gives the third, so reports carry all three.

What counts as one occurrence differs by platform. Some count the moment the ad is loaded into the page; others count only ads at least half visible on screen for more than a second. Counting the second way puts the number 20 to 30 percent lower for the same campaign. So two reports from different channels get their counting rules aligned before being placed side by side.

Paired with spend it becomes a unit price. The common measure is cost per thousand impressions: a budget of $2,300 producing 240,000 impressions works out to about $9.60 per thousand. That figure is the price of impressions, and it says nothing about how many clicks or signups followed. A low unit price doesn't make a campaign good either — buy cheaply in places nobody looks and only this number moves.

"Impressions are 240,000 and reach is 80,000. That's the same people three times over."

Separating occurrences from people.

"Creative that only lifts impressions means nothing. We need to see clicks."

This number alone can't judge performance.

"Don't just add impressions across two channels. They count differently."

Aggregation rules vary by platform.

Ravi rewrote the report as three lines: impressions 240,000, reach 80,000, average three times per person. Grace's question had been about the second line, and the third line produced the conclusion that the same people were seeing it too often. Rather than cutting budget, the next campaign widened the targeting conditions.