When you come across an ad, you form a certain image in the mind. Ad impression plays an important role in determining the efficiency of the ad; it is a single occurrence of a single advertisement appearance. A basic or gross impression is counted whenever the ad is viewed by the visitor. It also comprises of duplications and recurrent views. For example: if a web page contains 4 ads, 4 gross impressions will be counted. Whereas, only one unique impression is counted for every 24 hours, even if the same ads are displayed and viewed by the visitors a number of times. After a day, if someone views the same ad again, it is considered as another unique impression. The reports generated for unique impressions/IPs show the activities done by the visitors. Accurate unique impression counting is based on the information from the cookie stored on your visitors’ browser. In case the cookie is removed/deleted or disabled, a unique impression becomes similar to the gross/raw impression. The unique impression count will increase if the cookie is immediately cleared by the visitor.
The number of impressions formed is important to:
* The advertising sales people need to know the number of impressions available on the site, so that they don’t over or under sell.
* The marketers purchasing ads on your site want to know the number of impressions their particular ad, or set of ads, received.
* The marketers also consider the impressions of a campaign of ads across a variety of websites because that’s the measure of the effect of the ads on the marketplace.
For Instance
Visitor A viewed: Ad1, Ad2, Ad3, Ad1
Visitor B viewed: Ad2, Ad4
Counters:
Ad1 has 1 unique and 2 gross impressions
Ad2 has 2 unique and 2 gross impressions
Ad3 and Ad4 each has 1 unique and 1 gross impression
Relationship
The gross impressions are always greater than the number of unique impressions; the main reason behind this is that one user normally views more than one ad.
Similar terms
Other terms comprise of ad exposure, ad view or simply the impression. A gross impression will be the default term and is simply counted as an impression.
Intervals
The unique impression number of every ad is determined on the basis of the IP address of the visitor. If another ad server considers a unique impression per 12 hours, the unique numbers across the two reports will not be same.
Impressions vs Visits
When a visitor makes a single visit, it is termed as one single session. It is possible for the visitor to make multiple visits and thereby multiple page views can be generated. If the page contains multiple ad placements, the count of gross impressions will be higher as compared to the number of visits. For instance: if an individual visited your website twice on the same day, in the first visit, he viewed 3 pages, and saw 6 ads, while in the second visit he viewed 5 pages, and saw 10 ads.; therefore the number of gross impressions will be 16.
Unique visitors vs unique impressions
If the visitor views 20 pages, the website log/analytics will consider this as one unique visitor. However if 5 different ads are viewed by the same visitor while visiting those 20 pages, 5 unique impressions will be recorded for the same visitor, every ad counting for one unique impression.
