Gary Angel, one of the sharpest digital analytics practitioners, regularly cites the benefits of segmenting traffic in Google Analytics.

He says, “In every case, as you think about [specific metrics for your site], segmentation is an excellent first step for choosing the right explanation. If traffic for a site is rising, the first question I’d ask is 'With whom?' Is traffic rising for existing customers, for online only customers, or just prospects? If revenue is going up, I’d want to know exactly the same thing. Is revenue going up with all customers, or is it going up with customers who purchase high-end merchandise or is it up because we’re getting more customers?”

Angel’s points are well taken. Even for the most straightforward of ecommerce sites, with a basic implementation of Google Analytics, introducing segmentation to the analysis makes sense.

In this article, I will explore (a) potential ways to segment the traffic to your site in Google Analytics, (b) how to isolate those segments, and (c) what to look for in the data.

Accessing Advanced Segments

For any Google Analytics report, an "Advanced Segments" button appears just below the report name. Clicking this button opens a list of segments. You can select up to four of them, as shown below.

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To illustrate, the following image shows the ecommerce conversion rate for a site with three segments selected: New Visitors, All Visitors, and Returning Visitors.

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As is typical, returning visitors (orange line) convert at a higher rate than new visitors to the site (blue line). And, the overall conversion rate (green line) falls in between the two. Note that in Google Analytics, visitors can fall into multiple segments at once.

Default Segments vs. Custom Segments

Google Analytics includes a number of “default” segments. These cover the typical ways that traffic to websites can be meaningfully sliced. They cannot be edited or deleted, and their underlying configuration cannot be directly viewed. In most cases, that is fine. But, in some cases, the default segments can be ambiguous.

For instance, there is a Mobile Traffic segment. You may or may not expect tablets — such as the iPad — to be included in this segment. In fact, Google does treat traffic from tablets as being “mobile,” but you can only determine this by selecting the segment and then viewing the "Audience » Mobile » Devices" report.

Custom segments, on the other hand, are defined by you, which means they can be tailored to analyze aspects of traffic to your site that are unique and specific. You control the exact definition of the segment. Custom segments are associated with your user account; they are not automatically available to other users. Thus, if you log in to your Google account and create a segment, no other users can see that segment unless you share the segment definition with them, and they create the segment themselves.

Both types of advanced segments — i.e., default and custom — are useful. I will address default segments in this article, and custom segments in a subsequent one.

Starting Point Metrics

Virtually any report in Google Analytics, including custom reports, can be segmented. And, reports can be viewed across multiple segments for easy comparisons.

While there are no absolutes when it comes to what metrics are “right” for any given site, when analyzing traffic segments for ecommerce sites, I look at the following to see how they compare to the overall site, as well as to other relevant or related segments.

• Visits. This is the relative magnitude of traffic that meets the segment criteria. In some cases, the metric itself may be informative — “We’re getting almost no returning visitors to our site!”. But, more often, it is simply a check to ensure that you are not deeply dissecting a set of visitors to your site who account for very little traffic.
• Bounce rate. The bounce rate will vary widely across segments. For instance, returning customers naturally bounce at a much lower rate than new visitors. Look at the bounce rate, consider the segment, and see if you can logically explain why that segment has a higher, lower, or similar bounce rate to the overall site and related segments. If you can’t, then additional analysis may reveal that you are underserving a potentially valuable segment and can make changes to the site to address the issue.
• Ecommerce conversion rate. Like bounce rate, the ecommerce conversion rate will vary widely across segments. While that is expected, assessing the degree to which the conversion rate varies, and whether it make sense, can be a starting point for deeper analysis.

Depending on the specifics of your site, there may be other metrics that should be on this list.

Once a segment is identified that warrants further exploration — either because a metric is surprisingly out of whack with other segments or the rest of the site, or simply because you believe there is an opportunity to improve the experience for that group of visitors — there are any number of reports that can be used for deeper analysis. A good set of starting points include.

• Traffic sources. Assuming your segment is not based on a specific traffic source, then assessing where traffic is coming from in that segment can be revealing. For instance, are new visitors finding the site primarily through paid search, organic search, or specific non-search campaigns you have run?
• Landing pages. Landing pages are where visitors enter your site. For most sites, the home page is the top point of entry, but specific segments often have top landing pages that differ. Consider the content on the top landing pages in the context of the specific segment to spark ideas for adjusting what content is presented and how.
• Flow visualization. Flow visualization is one of the new features in Google Analytics. What it shows – by segment – are the top overall “paths” through your site. Can you logically explain why a particular segment has a propensity to take the top paths shown in this report? If so, have you considered the content along these paths from the perspective of each segment? Are there opportunities to adjust the content to better serve a particular segment?

In the balance of this article, I'll address a number of segments – default and custom – that warrant consideration when digging into your site’s traffic. This list is not comprehensive, but it highlights some of the segments that I use most often on behalf of my clients.