What does Impression mean?
Advertising is often sold on a CPM basis and paid out on an RPM basis. These mean Cost Per Thousand Impressions and Revenue Per Thousand Impressions respectively. The difference between the two is the ad serving fees that an ad network charges – meaning the RPM is always lower.
What is an impression?
There are several types of impression:
- A Page Impression is the loading of the page itself.
- An Ad Impression is when an ad is loaded on a webpage.
- A Viewable Impression is an ad impression from above the fold.
- In social media an impression is when a post loads in a users feed.
In online advertising when the term impression is used, an ad impression is usually what is meant.
Impressions are used as they are easy to count. Servers keep logs of items they load. Therefore counting up the loads of ads, pages or posts is relatively simple.
However, just because a page loads an item, it doesn’t not mean that anyone has actually seen it. Ads are often delivered below the fold, making many ad impressions worthless. This is a situation which is being addressed by the ad industry, but is also somewhat self correcting.
In an attempt to make advertising more fair, viewable impressions are now being measured. These are impressions which appear at least 50% above the fold, and on screen for 2 seconds (definitions vary). Many Ad Networks offer CPvM deals to sell only this type of ad impression.
This is also a self-correcting problem in advertising, as below the fold ads perform badly. This means that they cost less, and therefore publishers are less willing to use them. Also, due to page loading speed being an ingredient of SEO, there are less ads per page in general, with these un-viewable ads being the first to go.
In Social Media this metric is frankly a mess. Efforts are being made to improve it all the time, but currently an impression in social media generally means the number of times something appeared in people’s feeds. As a user won’t necessarily see their whole feed, or will perhaps scroll through at high speed, this makes this number unreliable.
A social media version of viewable impressions is vitally needed to improve this metric.
What it looks like
This is a demonstration of how to count ad impressions versus page impressions.
Not to be confused with
Reach, which is a count of users seeing content, not the number of times seen.
Sessions, which is the number of times users have logged onto a site.
Find out more
Author: Justin Driskill
Justin is the founder of The Online Advertising Guide and a freelance Digital Projects Manager.