GA4 Custom Dimensions

Track custom data specific to your business.

GA4 tracks pageviews but not business context. Custom dimensions let you track which pricing tier, user type, or account status—the data that actually explains behavior. Here’s how to set them up.

What Custom Dimensions and Events Are

Events: Actions users take. GA4 tracks some automatically (page_view, scroll, click). You can include your own (plan_selected, feature_used, upgrade_clicked).

Custom dimensions: Attributes attached to users or events. “User is on the Pro plan” or “This event was from a logged-in user.”

Together, they let you answer questions like: “How many Pro users used the export feature last month?”

Custom vs. Standard Dimensions: When You Need Custom

GA4 already tracks dozens of dimensions out of the box—page title, source/medium, device category, country, browser. Before creating a custom dimension, check whether a built-in one already answers your question.

Use standard dimensions when: You want to know which pages get traffic (Page path), where visitors come from (Session source/medium), or what devices they use (Device category). These are already collected.

Use custom dimensions when: Your question involves business-specific context that GA4 cannot infer from pageviews. Examples:

• SaaS: “Do Pro users engage differently than Free users?” — user-scoped user_plan dimension
• E-commerce: “Which product category gets the most add-to-carts?” — event-scoped product_category on the add_to_cart event
• Content site: “Do logged-in readers scroll further than anonymous visitors?” — user-scoped login_status dimension
• B2B: “Which company size segment converts from trial to paid?” — user-scoped company_size dimension

A practical rule: if you find yourself exporting GA4 data and joining it with another spreadsheet to answer a question, that missing field should probably be a custom dimension. Send it at the source so the analysis happens inside GA4, not outside it.

Setting Up Custom Events

Option 1: Google Tag Manager (Recommended)

If you use GTM:

1. Create a new tag: GA4 Event
2. Set the event name (e.g., “plan_selected”)
3. Add event parameters (e.g., plan_name: “pro”)
4. Set the trigger (e.g., button click with specific text)
5. Test in preview mode, then publish

Option 2: gtag.js Code

If you’re adding tracking directly in code:

// When user selects a plan
gtag('event', 'plan_selected', {
  'plan_name': 'pro',
  'plan_price': 99,
  'billing_cycle': 'monthly'
});

Setting Up Custom Dimensions

In GA4 Admin:

1. Go to Admin > Custom definitions
2. Click “Create custom dimension”
3. Name it (e.g., “User Plan”)
4. Set scope: User (persists across sessions) or Event (just this event)
5. Set the event parameter it maps to

Then in your code, send the user property:

// Set user properties (persist across sessions)
gtag('set', 'user_properties', {
  'user_plan': 'pro',
  'signup_date': '2024-01-15'
});

Useful Things to Track

User-Level Dimensions

• Current plan/tier
• Account age
• User role (admin, member, viewer)
• Industry or company size
• Signed in vs anonymous

Event-Level Dimensions

• Which feature was used
• Content type viewed
• Form step completed
• Error type encountered
• A/B test variant

Custom Events Worth Tracking

• Key feature usage (export, share, create)
• Upgrade/downgrade clicks
• Support chat opened
• Video played
• File uploaded
• Integration connected

Analyzing Custom Data

Once you’re collecting custom dimensions:

• Segment reports: Add dimension as a filter (e.g., “show only Pro users”)
• Create audiences: Admin > Audiences > “Users where user_plan = pro”
• Funnel by dimension: See how conversion differs by user type
• Explore: Use free-form or funnel explorations with custom dimensions

Limits and Gotchas

• GA4 has limits: 50 custom dimensions per property, 50 custom metrics
• User properties take time to update (not instant)
• Historical data won’t have custom dimensions from before you set them up
• PII (emails, names) should NOT be sent to GA4

Confirming Dimensions Appear in Reports

• Custom dimensions are registered in GA4 Admin
• Values are being collected (verify in DebugView)
• Dimensions appear in reports and explorations
• Data makes sense and matches expectations

Sources

• Google – Custom Dimensions & Metrics in GA4
• Google – GA4 Developer Documentation
• Google – GA4 Events & Conversions