Visitors vs. Visits

Let us first distinguish how these two web analysis metrics are different:
Unique Visitors
A unique visitor is a metric referred to an individual who has visited a site for the first time within a certain time period. Say if the unique visitor could have visited a site 10 times in a week, but if the time period specifies unique visitors for that week, a single unique visitor will only be counted once for that week. Once that week is over, that unique visitor can be counted again for a new specified time period. The primary method of calculating unique visitors is by setting a persistent cookie on the visitor’s browser to uniquely identify the visitor. Cookie technology helps to avoid common pitfalls, for example, IP Pooling, caching, or tracking visitors behind a firewall, when counting unique visitors.

A visit begins when a person first views a page on your website. The visit will continue until that person stops all activity on the site for 30 minutes, or until the maximum visit length occurs, which is 12 hours. For example, if you visit a page on, you have one instance of a visit that lasts until you have incurred 30 minutes of inactivity. Closing your browser window does not automatically end the current visit. If you don’t view any pages for more than 30 minutes, and then resume viewing pages, then a new visit is registered. The maximum length of any visit is 12 hours. No visit is allowed to extend beyond that period. If additional activity occurs for a period longer than 12 hours, with no period of inactivity exceeding 30 minutes, the visit will be counted twice. The new visit is counted at the first page view after the 12 hour length has been exceeded. The 30 minute visit timeout period is an industry standard. It is used by most web analytics products and it is recommended by industry analysts.
Both numbers are important (although they may not be critical – depending on the outcomes you need to measure) and they provide similar information, but there are some important differences.
1) Every Visit represents an opportunity to persuade or convert a visitor to a customer.
2) Measuring visits is based on fairly established industry standards
3) Unique Visitors are less accurate than Visits - Most web analytics tools, in the absence of cookie setting, fall back on IP address and user agent. This introduces significant variability in your Unique Visitor counts and can skew your true site performance and reach.
4) Unique Visitors mask your true conversion opportunities - Unique Visitors are a superset of Visits and may represent multiple opportunities to convert a customer. As such, using Unique Visitors as the denominator in most performance calculations is actually overstating the effectiveness of your site. For example, if I visit a retail site 4 times in one week, and purchase twice - what is my conversion rate? If you use weekly unique visitors, my conversion rate is 80%. If you use visits, my conversion rate is 10%. Which is a better representation of site effectiveness? Clearly the 10% is much more valuable in understanding where your site may or may not be performing optimally. With the 10% conversion metric, I have the opportunity to analyze which visits did not convert…what happened? Is it a navigational issue? A cross-sell problem? Or perhaps a remarketing opportunity? If you used Unique Visitors, you’d never get this visibility.
Unique Visitors has often been viewed as one of the most strategic web metrics. Countless companies and site operators have insisted on knowing how many unique visitors came to their site on any given day. By contrast, Visits has largely been the neglected stepchild of web metrics. Most folks know it’s there, but many prefer to ignore it in favor of the more popular Unique Visitor metric. Generally speaking, a visit starts when someone reaches your website, and is considered complete after 30 minutes of inactivity. It is also commonly referred to as a “session”.
It is good to know how many people have come to your site, just as it is good to know how many people walk into your store in the mall. It gives you an idea of the total number of customers/potential customers that you are drawing in, and allows you to compare trends over time to spot opportunities or problems.
But there’s a big difference between a person poking their head into your store on their way to the food court, then never to returning again, and a person who repeatedly makes the trip to your store, even if they don’t purchase something every time. And this is where I think visits may provide more relevant, actionable information than visitors for this client.
It is interesting to know how many people visit the site and to hopefully see this grow over time, but more critical in this case is the number of visits. Now for sake of argument, let’s say you can only report one of these metrics to your executives - which is it going to be? Unique Visitors? or Visits?
Leaving aside the argument over whether either of these satisfies the criteria to become a real KPI, let’s consider the uses of each metric.
Let’s assume 5% of your visitors delete cookies…that would imply a 5% level of inaccuracy around unique right? Wrong. The fallback method for unique visitor determination is most commonly IP and user agent string - a *much* less reliable approach than cookies. This was actually a key reason log file solutions fell out of favor - because most relied on IP and user agent and hence were highly inaccurate. Because of the inaccuracy of user and IP agent, your 5% of cookie rejecting visitors can actually skew your traffic numbers by many times over. So you may find that your 5% is actually 15% of your unique visitors. And because it’s nearly impossible to reconcile this number (outside of triangulating with registered user counts), you have little hope in relying on unique visitors as a true measure of “visitors”.
Furthermore, assuming you can set a persistent cookie, you’re only measuring a computer - not a person. Multiple people use single computers. Single people use multiple computers. So what is your true unique visitor count?
You see, a single visit could, and very likely, result in multiple hits and page views.
If you left and came back in an hour, it could count as another visit but not another visitor. That’s where it gets a little more complicated. Things that must be considered are how long you were inactive and how long it took you to come back.
There’s more. In order to count as a unique visitor, the visitor must have a browser that accepts cookies.
OK, the truth is, they can both help you so depending on who you ask, you might get a different opinion. If one is reporting on Visits then he doesn’t have to worry about whether or not a user’s browser accepts cookies. But ultimately, it’s more valuable to look at visits since those numbers include repeat visitors.
So the number of visitors is interesting, the number of visits may be more so, but we need to get to the real reason our site exists: conversions. In this case, purchases. And to make decisions about optimization and resource allocation, we need to understand the efficiency of various channels bringing visits to our site and this means: conversion rate. And to get a conversion rate that makes sense, we need to have the most appropriate denominator.
Which brings us back to visitors vs. visits? Yes, it can be useful to know what percentage of unique visitors in a month made a purchase, but wouldn’t it be more useful for site selling repeat purchase products – to know the percentage of visits that resulted in a purchase?