What is an ad impression

I’ve blogged previously about [various] [page-view] [Web] [visitor] [analytics] [visit] [terms] [pages-per-visit]. Almost all of those would be described as **audience** terms — they describe how people are viewing your site.

Let’s take a stab at some **revenue** terms, starting with:

**What’s an ad impression?**

It’s a measure of the number of times an ad is seen by a user. In that sense it’s almost like a [page view] [page-view], except it only refers to a portion of the page — where the ad is.

The number of impressions is important to several different sets of folks.

* The advertising sales folks need to know how many impressions are generally available on the site, so that they don’t over or under sell.

* The marketers buying ads on your site want to know how many impressions their particular ad, or set of ads, received. They’re likely paying for a set number of impressions and they want to make sure they weren’t undersold.

* The marketers also care about the impressions of a campaign of ads across a variety of sites because that’s a measure of, roughly, how much effect the ads should have on the marketplace. Just as page views are impression of a piece of content’s influence on the marketplace.

An page can contain multiple ads and thus serve multiple impressions per page view. Why would a site put multiple ad units on a page? It’s all about [CPM] [cpm], but we’ll tackle that one [another time] [cpm].

[page-view]: /blog/2008/11/13/what-is-a-page-view/ “What is a page view?”
[visitor]: /blog/2008/11/18/what-is-a-visitor/ “What is a visitor?”
[visit]: /blog/2008/11/19/what-is-a-visit/ “What is a visit?”
[pages-per-visit]: /blog/2008/11/20/what-are-pages-per-visit/ “What are pages-per-visit?”
[cpm]: http://heisel.org/blog/2008/11/30/what-does-cpm-mean/