Dimension
A dimension is a qualitative attribute of your data that describes the characteristics of users, sessions, or events. It answers “who,” “what,” and “where,” not “how many.” Examples include Country, Device category, Page path, and Source. In analytics reports, dimensions form the rows that you break your numbers down by.
Dimensions vs Metrics
Dimensions describe data. Metrics count it. That single distinction is the most important thing to understand in analytics reporting.
A dimension is a category or label, like City or Browser. A metric is a number, like Sessions or Conversions. Every standard report pairs the two: dimensions become the rows, metrics fill the columns.
Take one row of a GA4 report: “United States | 4,210 sessions.” Here “United States” is a value of the Country dimension, and “4,210” is the Sessions metric. Change the dimension to Device category and the same sessions split across “desktop,” “mobile,” and “tablet” instead.
| Dimension | Metric | |
|---|---|---|
| Answers | Who / what / where | How many / how much |
| Data type | Text, category | Number |
| Report position | Rows | Values |
| Examples | Country, Source, Page path | Sessions, Users, Revenue |
A quick test: if you can count it, it is a metric. If it labels or groups the count, it is a dimension.
Common Dimension Examples
Analytics tools ship with dozens of predefined dimensions. The most used ones fall into a few groups:
- Acquisition. Source, Medium, Campaign, Default channel group. These show where traffic came from.
- User. Country, City, Language, Age, Gender, New vs returning.
- Technology. Device category, Browser, Operating system, Screen resolution.
- Behavior. Page path, Landing page, Event name, Page title.
- Time. Date, Hour, Day of week.
Your campaign tracking feeds these directly. The values in your UTM parameters populate the Session source, Session medium, and Session campaign dimensions in GA4. Tag a link with utm_source=facebook and “facebook” becomes a selectable value under the Source dimension.
Types of Dimensions
GA4 sorts dimensions into two broad categories.
Default dimensions are built in and collected automatically. Country, Device category, and Event name need no setup. They cover most everyday reporting.
Custom dimensions capture data unique to your business that GA4 does not track by default, such as membership tier, author name, or logged-in status. You create them from event or user parameters. GA4 assigns each a scope:
- Event-scoped. Tied to a single event (for example, the article category of a page view). Standard properties allow up to 50.
- User-scoped. A persistent attribute of the user, like account type. Standard properties allow up to 25.
- Item-scoped. Tied to a product in ecommerce data, like item brand or color.
How to Use Dimensions
Add or change a dimension to slice the same metric in different ways without altering what you measure.
- In a GA4 standard report, use the search-style dropdown under the table to swap the primary dimension.
- Add a secondary dimension to cross-tabulate, for example Country broken down by Device category.
- In the Explore section, drag dimensions onto Rows and metrics onto Values to build a custom table.
If you tag campaign links, linkutm’s analytics dashboard shows click data by source and campaign alongside your GA4 reports, so your dimension values stay consistent across both.
Cardinality and the “(other)” Row
High-cardinality dimensions can corrupt your reports. Cardinality is the number of unique values a dimension holds.
A dimension like Page path on a large site can have hundreds of thousands of unique values. When a GA4 report exceeds its row limit, GA4 groups the excess into a single “(other)” row, hiding the detail. Avoid pushing unique IDs (like user or transaction IDs) into dimensions for this reason. Use the Explore reports or the GA4 API, which handle higher cardinality, when you need that granularity.
Frequently Asked Questions
What is a dimension in analytics?
A dimension is a qualitative attribute that describes your data, such as Country, Source, or Device category. It groups and labels your numbers rather than counting them. In a report, dimensions appear as rows and define how a metric is broken down.
What is the difference between dimensions and metrics?
Dimensions describe data; metrics measure it. A dimension is a category like City or Browser, while a metric is a number like Sessions or Revenue. If you can count it, it is a metric. If it labels the count, it is a dimension.
Is “Source” a dimension or a metric?
Source is a dimension. It labels where a visit came from, such as “google” or “facebook,” and it carries no number on its own. The metric paired with it, such as Sessions or Users, supplies the count.
What is a custom dimension in GA4?
A custom dimension captures data GA4 does not track by default, like membership tier or author name. You build it from an event or user parameter and assign it a scope: event, user, or item. Standard properties allow 50 event-scoped and 25 user-scoped custom dimensions.
To see your campaign sources and metrics in one place, explore linkutm’s analytics dashboard.