What is a Dimension in Google Analytics?

Making sense of Google Analytics often feels like learning a new language, filled with specific terms that can be a bit confusing at first. But a huge part of becoming fluent comes down to understanding two core building blocks: dimensions and metrics. Once you grasp how these two concepts work together, the data in your reports will start telling a much clearer story.

This tutorial will demystify what a dimension is in Google Analytics. We'll explore where to find them, which ones are most useful, and how to combine them to uncover valuable insights about your website traffic and user behavior.

Dimensions vs. Metrics: A Simple Explanation

The easiest way to think about dimensions and metrics is to picture a simple spreadsheet. The textual descriptions in your rows are your dimensions, and the numbers in your columns are your metrics.

• A Dimension is a descriptive attribute or characteristic of your data. It describes what, who, or where. In short, dimensions provide context. A dimension will almost always be a word, not a number.
• A Metric is a quantitative measurement. It's the number that tells you how many or how much. Metrics are the numbers you use to measure a dimension.

This is a foundational concept in all data analysis. You can't have one without the other. Reporting "450" is meaningless without knowing if that’s 450 users, pageviews, or clicks. Similarly, knowing your city is "New York" is just a fact until you attach a number to it, like "New York: 450 users."

Let’s look at a concrete example right from the Google Analytics interface. A standard report looks something like this:

Example: The Traffic Acquisition Report

When you look at a report showing where your traffic came from, you'll see a table. The first column usually contains the dimension, and the following columns contain the metrics associated with that dimension.

In the Acquisition > All Traffic > Source/Medium report, your primary dimension is Source / Medium.

• Dimension (the "what"): google / organic
• Metrics (the "how many"):

The dimension, google / organic, tells you the origin of the traffic. The metrics like Users and Sessions quantify the amount of traffic that came from that specific dimension.

Common Types of Google Analytics Dimensions You'll Use Daily

Google Analytics offers dozens - if not hundreds - of pre-defined dimensions. You don't need to know all of them, but you should become very familiar with a core set. They typically fall into a few intuitive categories.

1. Acquisition Dimensions

These dimensions tell you how users found your website. They answer the question, "Where is my traffic coming from?" This is essential for understanding which marketing channels are working.

• Source: The specific origin of your traffic. Examples: google, facebook.com, newsletter.
• Medium: The general category of the source. Examples: organic (unpaid search), cpc (cost-per-click, or paid search), referral (a link from another site), email.
• Campaign: The name of a specific marketing campaign, which you can set with UTM tracking codes. Examples: summer_sale_2024, may_newsletter.
• Keyword: The keyword the user searched for to find your site. (Note: Due to privacy, this is often listed as (not provided) for organic search, but it’s still valuable for paid search campaigns.)

Mixing and matching Source and Medium (google / organic vs. google / cpc) gives you a clean separation between your SEO and paid search efforts.

2. Audience/User Dimensions

Instead of "how," Audience dimensions answer the question, "Who is visiting my site?" Understanding your audience’s characteristics helps you tailor your content and user experience.

• Device Category: Shows whether a user is on Desktop, Mobile, or Tablet.
• Browser: The web browser used. Examples: Chrome, Safari, Firefox.
• Country / City: The geographic location of your users.
• Language: The browser language setting of the user.

For example, if you see that 80% of your audience visits on Mobile, it confirms that having a responsively designed website is non-negotiable.

3. Behavior Dimensions

Behavior dimensions answer the question, "What did users do after they arrived?" They help you understand which content on your site is the most engaging.

• Landing Page: The first page a user saw when they arrived on your website during a session. This is an extremely useful dimension for understanding which pages are your main entry points.
• Page: Any page a user viewed on your site.
• Page Title: The title of the page they viewed (e.g., "What is a Dimension in Google Analytics? - Our Blog").
• Exit Page: The last page a user viewed before leaving your site.

By analyzing Landing Page, you can see which blog posts attract the most organic traffic or which product pages are the most effective at drawing people in from ads.

The Real Power: Pairing a Primary Dimension with a Secondary Dimension

Here’s where Google Analytics reporting starts to move from basic facts to actionable insights. Most standard reports start by showing you one dimension at a time - the Primary Dimension. But the most valuable analysis often happens when you add a second layer of context - a Secondary Dimension.

A secondary dimension lets you split the data in your table into more granular rows. Let’s walk through a practical scenario.

Scenario: You want to know not just where your traffic comes from, but which devices those users are on.

1. Start with your primary dimension. Go to Acquisition > All Traffic > Source / Medium. You see a list of your top traffic sources. This is interesting, but it's very high-level.

Your primary dimension is Source / Medium, showing rows like:

• google / organic
• facebook.com / referral
• direct / none

1. Add a secondary dimension. Just above the data table in Google Analytics, you’ll see a dropdown button that says “Secondary dimension.” Click this and a search box will appear.

Type in and select Device Category.

1. Analyze the deeper insight. Your report instantly updates. Now, each Source / Medium row is broken down by the user's device. Your table now looks something like this:

• google / organic: Desktop
• google / organic: Mobile
• facebook.com / referral: Desktop
• facebook.com / referral: Mobile

This reveals a more detailed story. For instance, you might discover that google / organic traffic is 90% mobile, while your direct / (none) traffic is 70% desktop. You also might see that your mobile visitors have a much lower e-commerce conversion rate. This kind of insight allows you to take action, such as investigating your mobile checkout experience for potential friction points.

Some of my favorite secondary dimension combinations:

• Primary: Landing Page | Secondary: Device Category. ([Shows which pages are popular on mobile vs desktop.)
• Primary: Source / Medium | Secondary: City. ([Reveals your best marketing channels in specific locations.)
• Primary: Device Category | Secondary: Landing Page. ([Identifies your site's main entry points for mobile users specifically.)

Taking It Further: Custom Dimensions

While default dimensions cover most reporting needs, sometimes you need to track data that is specific to your business - data Google wouldn't know about otherwise. This is where custom dimensions come in.

A custom dimension allows you to send your own unique data to Google Analytics and use it to describe and segment your traffic.

Why would you need this?

• For a content website: You could create a custom dimension named Post Author to see which writers drive the most traffic and engagement.
• For a SaaS application: You might use a User Status dimension to distinguish between logged-in and logged-out users or Free Plan vs. Pro Plan users.
• For an e-commerce store: You could create a Customer Tier dimension to see if VIP Members behave differently than regular customers.

Setting up custom dimensions requires a bit more technical work (usually involving Google Tag Manager to send the right data to GA), but they allow you to enrich your analytics with business-specific context, making your reports immensely more powerful.

Final Thoughts

Understanding dimensions is one of the most important steps toward mastering Google Analytics. Once you know that dimensions describe your data and metrics measure it, you can begin combining them with secondary dimensions to get past high-level vanity metrics and uncover the real story of what’s happening on your site.

Of course, the challenge grows when your data is spread across multiple platforms. Tying dimensions like utm_campaign in Google Analytics to your Campaign Name in Facebook Ads and then to actual revenue numbers in Shopify often requires hours of tedious work in spreadsheets. For that, we built Graphed. Our platform automatically brings all your marketing and sales data into one place, allowing you to ask questions in plain English - like "Compare Facebook ad spend vs. Shopify revenue by campaign for last month" - and instantly get a real-time dashboard, so you can spend less time wrangling data and more time acting on it.