Google Analytics Audit Test #

40

Capturing First-Party User ID or Email

Why It Matters:

Critical to understanding user journeys that span multiple sessions or periods longer than 30 minutes.

Industries:

All

Checks For:

Utility

How powerful is your current implementation?

Insight Category:

Behavior

Can you tell what visitors are doing?

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Background

A GA4 audit is essential for uncovering missing insights—key data points that organizations don't yet know and can act upon. A well-done audit evaluates both behavioral tracking and traffic attribution, ensuring each is accurate and useful. It also assesses whether the data collected truly supports business decisions and reporting.

Test Detail

This test checks whether your GA4 implementation is capturing a first-party User ID—a unique, persistent identifier generated by your system (CRM, login system, account ID) and passed into Google Analytics (GA4) to unify user activity across sessions and devices.

Without a User ID strategy, you’re limited to Google Analytics default client-based identifiers (cookies), which can’t:

  • Accurately connect logged-in users across browsers or devices
  • Stitch together multi-session or cross-platform behavior
  • Enable precise cohort or LTV analysis
  • Support reliable user-level audience building

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Google Analytics audit test results.

How to Conduct This Test

Basic Tests

  • In GA4 > Admin > Data Streams > More tagging settings > User-ID, confirm that User-ID is enabled
  • In GA4 DebugView, log in as a known user and check if user_id appears with the correct value

Advanced QA

In BigQuery, run the following query:

    SELECT user_id, COUNT(DISTINCT session_id) as sessions
    FROM `your_dataset.events_*`
    WHERE user_id IS NOT NULL
    GROUP BY user_id
    ORDER BY sessions DESC
  • Are user_id values consistently present? Are they meaningful?
  • If user_id is missing, inconsistent, or based on device/client ID, tracking is likely incomplete

Automated, Free Audit

Not sure if your user identity data is showing up? Run our Instant Audit

Or hire a pro to help implement User ID tracking correctly.

How To Fix

  • Generate a first-party User ID from your site or app’s authentication system (e.g., customer ID, account ID)
  • Pass the User ID into GA4:
  • In GTM: Set it as a user property using a variable (e.g., from a data layer or cookie)
  • In hardcoded GA: Set user_id with gtag('config', 'GA_MEASUREMENT_ID', { user_id: 'YOUR_ID' })
  • Enable User-ID support in GA4 Admin, if not already turned on
  • Ensure the User ID is never PII (e.g., not an email address) and complies with privacy regulations
  • Monitor sessions with and without User ID to improve identity resolution over time
  • Hire a pro to deploy a secure and consistent User ID solution that unlocks long-term user insights and better audience strategies.

Tips from a Google Analytics Consultant

Focus on Insights

Every Google Analytics audit should result in a plan for more insights.

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An insight is:

  • something you don't know
  • and can act on to improve performance

The Goal

Identify and remove insight blockers. Don't get tempted to track things you can't act on!

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