WEB STATS: The difference between hits, page impressions, user sessions and unique visits
EVERYONE with a website or blog should be interested to know just how well they are doing in terms of generating online traffic. However, the value of website statistics lies in the interpretation of trends rather than concentration on precise figures.
While some site aggregators focus on ‘hits’ and ‘user sessions’, others offer insight into ‘unique visits’ and ‘page impressions’. Below is an attempt at distinguishing between these terms in order to better understand what the dots and lines on web statistics mean.
The idea of measuring website traffic using hits is becoming rather old school due to its inaccuracy. Technically speaking a page hit is the term for any requested file, including each of a page’s images or graphics. It is the retrieval of any item, like a page or a graphic, from a web server. Any time a piece of data matches criteria you set, in a Google search for example, it’s recorded as a hit.
The problem with hits however is that when a visitor calls up a web page consisting of several graphics, each one is recorded as a hit plus one for the html page. For this reason, hits often aren’t a good indication of web traffic.
While a hit is a single file request from a web-server, a page impression is a combination of one of more files sent to a user via that user’s request (such as a search). In other words, it is the viewing or downloading of a website in its entirety by one user.
In web advertising, the term ‘impression’ is often synonymous for ‘view’, and is usually what advertisers use to determine how and where to advertise online.
However, the accuracy of this data will depend upon whether or not the user’s PC is ‘caching‘ the files integral to that page, or whether the user clears the cache after each session. In other words, whether or not the page has to reload each time.
Page impressions therefore become meaningless on framed sites. If a framed page has a separate frame for the header, the top border and the main text area, for example, a visitor will create a total of four different page impressions rather than one.
In tabulating more accurate statistics for website usage, user sessions are often used for counting the number of times a particular user visits the site. This is determined by the visitor’s IP address and thereby solves the problems of repeat visits to pages.
These are calculated by the presence of a user with a specific IP address who has not visited the site recently (typically, anytime within the past 30 minutes). For example, a user who visits a site at noon and then again at 3pm would be counted as two user sessions or visits.
A related term for user sessions, a unique visitor refers to a person who visits a website more than once within a specified period of time.
Different from a hits or page views (measured by the number of files that are requested from a site) unique visitors are measured according to their unique IP addresses. These act like online fingerprints, and unique visitors are counted only once no matter how many times they visit the site.
One could think of unique visitors as your loyal readership or website users. Treat them well!
Hope this was helpful. Please add any additional insight or info you may have below.