← DictionaryImpression Share
The share of available ad impressions your ads actually received.
How much of the available space you got.
What It Is
Impression Share belongs to Marketing, specifically the Paid part of it. The canonical meaning is the share of available ad impressions your ads actually received.
It is something measured and compared over time, so one reading in isolation tells you almost nothing. Used with that meaning, it stays a working tool rather than a talking point.
How It's Used
Impression Share earns its keep in campaign planning, channel choices and the reporting that follows them. It rarely travels alone — expect it next to Impressions, Ad Spend and Bid Strategy. The practical test is whether it is measured the same way each period, against something.
Why It Matters
The cost of being vague about Impression Share shows up later, not today. When it is unclear, spend keeps moving but nobody can say what it bought. The businesses that treat it seriously spend less time redoing work.
Think of a weighing scale — useful because you step on it more than once. How much of the available space you got.
Termshift™
How the meaning shifts depending on who is using it, and where.
In agency and in-house rooms, Impression Share means exactly the share of available ad impressions your ads actually received.
In plain conversation it comes out as how much of the available space you got.
The Bottom Line
The practical takeaway on Impression Share: how much of the available space you got. Judge it by that, not by how it sounds.