Digital Marketing Measurement

Measuring reach – Key metrics for web traffic measurement

In today’s online advertising landscape, measurement is critical for both publishers and advertisers/media buyers.

Advertisers want verifiable, comparable metrics to guide their advertising campaigns, in order to identify the web content that best allows them to reach their target audience and maximize ROI on advertising spend.

Publishers need to be able to gain advertisers’ trust through transparency of data and at the same time have interest in monitoring advertising’s performance on their properties to identify the best ad formats and implementations as well as the best fitting ad inventory.

The problem is that often advertisers and publishers don’t use the same measuring tools and systems. However, there are key metrics, common units of measurement that allow both parts to talk the same language.

The fundamental questions that digital marketing measurement tries to answer are essentially two:

Audience: who are they?

Reach: how many are they?

Let’s start with the second.


There are several tools to measure reach, such as Google Analytics and Website logs, but let’s firstly have an overview of the most common key metrics in use.

– Hits

Hits have been ironically redefined by many as “How Idiots Track Success”. Let’s see why.

A hit is a request to a web server for a file. Each file sent to a browser by a web server is an individual hit. When a user visits a web page with their browser, not only will the browser send a request to the server hosting that page for the html file itself, but it will generate also an individual hit (an individual request) for each file that page is made of (images, embedded videos etc).

Because of this, hits can’t be considered reliable to measure web traffic, because for a single page view (or page impression), many hits may be registered.

– Page views or Page impressions

A page view, instead, is a request to load a single web page as a whole, regardless of how many files the page is made of and how many hits are generated.

As explained in Google Analytics support website, it is important to note that “if a visitor clicks reload after reaching the page, this is counted as an additional pageview. If a user navigates to a different page and then returns to the original page, a second pageview is recorded as well.”

– Visitors or unique visitors

Visitors or unique visitors are the number of unique individuals visiting a site (as a whole, not specifically a single web page within the site).

A unique visitor is usually identified via an anonymous cookie. It is important to note that this is usually only a close estimate, not an exact measurement, as there are many scenarios that can cause imprecision, such as:

– Two people visiting a site using the same computer and same browser will be identified by the same anonymous cookie and therefore counted as one unique visitor.

– One individual visiting the same site from two different computers will be issued a cookie on each computer and therefore counted as two unique visitors

– An individual visiting a site from the same computer but using two different browsers will be counted as two different visitors, because each browser will be issued its own cookie.

– If an individual visits a site and is issued a cookie, but then visits the same site again after having cleared their cookies, that same individual will be issued a new cookie and counted as a different visitor on that second visit (therefore counted as two different unique visitors).

Unique visitors are calculated over a defined period of time or reporting timeframe (e.g. day, week, month, years etc), but it is essential to note that individual visitor counts from different periods can’t be simply added up to get an overall visitor count.

If I count my visitors on a daily basis, for instance, I can’t simply add up my visitor counts for the 7 days of the week to get the overall weekly visitor count. An individual tracked as unique visitor on Monday could return on Tuesday and be tracked again as unique visitor, therefore my weekly addition would result in an inflated number.

Visits or sessions

In web analytics terms, a visit (or a session) starts when a visitor starts interacting with a site (typically the first page view by the visitor) and ends when a specified period of time elapses since the last interaction of that visitor with the site.

In most web analytics tools a visit ends after 30 minutes of visitor’s inactivity on the site, but this can vary and can be personalized.

If the time limit of a single visit/session is set at 30 minutes and one visitor leaves your site but then returns to it within 30 minutes, that will be counted as one single visit/session, whereas if the same visitor leaves and return after 30 minutes, that will be counted as a second visit/session.

Differently from unique visitors, the number of visits to a site can be summed up across different periods of time to get an overall visit count.

It is important to underline that a visitor accessing a site for the first time is counted as a new visitor and a new visit. If the same visitor returns to the site a second time (without having deleted their cookies and accessing the site from the same computer/browser/device) after the set session time has elapsed, that will be counted as a new visit, but not as a new visitor.

New and returning visitors

We have mentioned how counting unique visitors can only be an approximation because of the problems related to cookie tracking. This is also a reason for caution in the assessment of new visitors vs returning visitors.

If I visit a website and later on return to it (in a different visit/session), the cookie that was issued to me on my first visit identifies me as a returning visitor.

However, if I do that after having deleted my cookies or if I visit that site from a different device/computer or a different browser, I will be issued a new cookie and identified as a new visitor. This is why statistics on new visitors tend to give overestimated numbers.

In conclusion, there is a good range of key metrics to measure web traffic, but these metrics don’t say much about who our audience is, who is behind the browser. This will be the topic of my next post.


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