Secondary dimensions in GA4 (and in Universal Analytics as well) are a critical tool to help you get more insight from your data. They allow you to break down your primary dimensions into meaningful and relevant data. They transform the way you analyze primary dimensions and gain information.

We’ll explore what secondary dimensions are as well as the benefits to using them in your reporting and analysis efforts.

What Are Secondary Dimensions?

Secondary dimensions break down each line of primary dimension data so that you can get a better understanding of what exactly you’re looking at in more granular chunks. You will be able to view the primary dimension within a table split out by an additional dimension of data within the same table. This gives you the opportunity to get so much more value and data from a single table. 

Using Secondary Dimensions

Adding a secondary dimension to your GA4 table report take just a few clicks. You’ll want to start out in a table report, such as the User or Traffic Acquisition report, the Pages and Screens report, or the Events report. In this example, I’ve chosen to take a look at traffic acquisition. This will describe how users are directed to my website and from where.

Next, you’ll click the plus icon at the top right hand corner of the primary dimension field. This will open up the dropdown menu to choose a secondary dimension. You can either use the search field or click through one of the categories of dimensions in order to find the one you’re interested in. Note that if you have set up Custom Dimensions, you can choose those as a secondary dimension under the “Custom (Event-scoped)” or “Custom (User-scoped)” categories.

You can then choose the secondary dimension you want to analyze with and that will load new information as each row of data and line item is broken down. Since each item in the primary dimension is being broken down by a secondary dimension, the overall number of rows in the report will grow, so you may want to choose to expand how many lines of data you want to be able to view so that you can quickly browse through the table.

As you can see in the above screenshot, when I break my traffic acquisition report which has a default primary dimension of ‘Default channel grouping’ down by source/medium, I get much more detailed info about how users are navigating to my site. For example, I can see that I’m getting traffic from multiple different email sources (some of whom better identify themselves with the utm_source parameter than others, such as Aleyda Solis’ #SEOFOMO). 

For another example, in the below screenshot, I’ve broken down the Pages and Screens report by a dimension of Device Category which allows me to see, by page, which devices people are using to visit my site. Looks like all of my topped viewed blog posts happen on a desktop device.

How can Secondary Dimensions help you?

Secondary dimensions can and should change the way you look at reports. Simply looking at an out of the box report is often too high level, or doesn’t offer enough insight in and of itself. It’s great to know how many people came to your sight by different channels such as Paid Search, Organic Social, etc. But maybe there is a difference in how they interact with your site (ex. Complete a conversion event such as a purchase) depending on which device they are on. You can use a secondary dimension of device type to get that more granular level of detail!  Breaking down your data by additional dimensions can help you make more targeted marketing decisions based on granular user or traffic data. 

This information helps make important marketing and business decisions. You can quickly get a handle on things like which social media sites and campaigns are driving traffic to your website and you can then use this information to optimize your marketing efforts. 

By now, hopefully you see that secondary dimensions can be extremely beneficial. If you want to see an overview of using secondary dimension in the GA4 user interface, then take a quick look at my YouTube clip below. I’ll be exploring the secondary dimensions and how they can help me sort through a variety of data.

You can learn even more about Google Analytics 4 by simply visiting https://ksdigital.co/academy/  where you can explore several courses designed to up level your digital analyst skillset and help you master GA4.