How to Add Secondary Dimension in Google Analytics 4

Seeing that your website got 10,000 visitors from the United States is useful, but it doesn't tell you the whole story. To get real insights, you need to know more: Which cities are they from? Are they using their phones or desktops? How did they find your site in the first place? Answering these questions requires adding a second layer of detail to your reports, and that’s exactly what secondary dimensions in Google Analytics 4 are for. This article will walk you through what secondary dimensions are and exactly how to use them in both your standard GA4 reports and custom Explorations.

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First, What Exactly Is a Secondary Dimension?

Before clicking any buttons, it helps to understand the basic building blocks of any analytics report: dimensions and metrics.

• Metrics are the numbers. They are the quantitative measurements like Users, Sessions, Conversions, or Revenue. They answer the question "how much?"
• Dimensions are the labels or categories that describe your data. They are non-numerical and answer questions like "who," "what," "where," and "how." Examples include Country, Device category, or Session source / medium.

In any standard report, the main dimension you see listed in the first column is your primary dimension. For example, in the Traffic Acquisition report, the primary dimension is usually 'Session default channel group,' showing you rows for Organic Search, Direct, Paid Search, etc.

A secondary dimension is simply a second dimension you add to the report to further break down the primary one. It provides an additional layer of context, splitting each row of the primary dimension into more granular sub-rows.

For example, if your primary dimension is Country, you could add Device category as a secondary dimension. Your report would then transform from this:

• United States: 10,000 Users
• Canada: 2,000 Users

Into this:

• United States
• Canada

This simple addition immediately uncovers new insights. In this case, you can now see that the US audience has a higher proportion of mobile users compared to the Canadian audience, which might influence your advertising strategy.

Adding a Secondary Dimension in Standard GA4 Reports

For quick analysis and day-to-day checks, using secondary dimensions in GA4’s built-in reports is the fastest way to get answers. The user interface makes this incredibly simple.

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Step-by-Step Instructions

Let's use a common scenario: you want to see which specific URLs are driving traffic from organic search.

1. Navigate to a Standard Report: From the left-hand menu in GA4, go to Reports → Acquisition → Traffic acquisition.
2. Locate the Plus Icon (+): Look at the main data table in the report. The very first column header will be the primary dimension (e.g., 'Session default channel group'). Right next to this header, you’ll see a small blue plus icon. This is the button to add a secondary dimension.
3. Select Your Secondary Dimension: Click the plus icon. A dropdown menu will appear with a search bar and a list of available dimensions categorized by topic (e.g., 'Page / screen', 'Traffic source', 'Geography').
4. Find and Click: You can either scroll to find the dimension you need or use the search bar. For our example, type "Landing page" into the search bar and select Landing page + query string.
5. Analyze Your New Report: The report table will instantly refresh. A new column will appear next to the primary dimension, showing the secondary dimension you just added. Now, you can scroll down to the 'Organic Search' row and see a line-item breakdown of every unique landing page that brought in users from organic channels, along with all the associated metrics like Users, Sessions, and Conversions.

And that’s it! In five clicks, you’ve gone from a high-level overview of your traffic channels to a specific, actionable list of your top-performing SEO content.

Using a Second Dimension in GA4 Explorations

While standard reports are great for quick-fire questions, they have limitations on how many dimensions you can combine and how you can visualize the data. When you need more flexibility and power, GA4's 'Explore' section is the place to be. Explorations allow you to build fully custom reports from scratch.

Step-by-Step Instructions for a "Free form" Exploration

Let's build a report to see which marketing campaigns (source/medium) perform best on mobile vs. desktop.

1. Go to the Explore Section: Click on Explore in the left-hand navigation pane and start a new, blank 'Free form' exploration.
2. Import Your Dimensions and Metrics: An exploration starts as a blank canvas. You have to tell it what data to make available.
3. Build the Report Structure (Tab Settings): Now, you'll use the Tab Settings column to tell GA4 how to arrange the data you just imported.
4. Analyze the Exploration: The canvas on the right will now show a detailed table with your campaigns (Source / Medium) as the rows and device types (Desktop, Mobile, Tablet) as the columns. You can instantly compare session volume and conversion performance across every campaign and device combination, spotting opportunities for optimization in seconds. For example, you might discover that a Google Ads campaign drives tons of mobile traffic but only converts on desktop, indicating a problem with your mobile landing page.

Explorations are far more powerful because you can add more dimensions, apply advanced filters, change visualizations, and save the report for future use.

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Creative Ideas and Pro Tips

Simply knowing how to add a secondary dimension is just the start. The real skill is in knowing which combinations will answer your most important business questions. Here are a few invaluable combinations to try:

• For Content Strategy:
• For E-commerce Analysis:
• For Geographic Targeting:
• Use Filters Liberally: Remember that you can apply filters on top of your primary and secondary dimensions. For instance, in an Exploration, you could filter for only 'Mobile' traffic, then set your primary dimension to 'Country' and your secondary to 'Landing Page' to see what the most popular entry points are for on-the-go users around the world.

Final Thoughts

Getting comfortable with secondary dimensions is one of the fastest ways to level up your skills in Google Analytics 4. It's the core technique for moving beyond surface-level metrics and discovering the specific, actionable insights that truly drive business growth, whether that's through analyzing standard reports or building custom Tables in Explorations.

Of course, even with GA4's tools, answering complex business questions can often feel like a time-consuming scavenger hunt. That’s why we built Graphed. Instead of clicking through menus and manually building reports to figure out which landing pages are converting best for mobile traffic from Facebook campaigns, you can simply ask a question in plain English. We connect your data sources - like Google Analytics, Shopify, and your ad platforms - and generate real-time dashboards and reports in seconds, enabling you to get straight to the insights without all the manual work.