Google Analytics Audit Test #

23

(not set) medium

Why It Matters:

Critical to understanding where your traffic is coming from and assigning appropriate credit.

Industries:

All

Checks For:

Accuracy

How accurate is your recent data?

Insight Category:

Attribution

Can you tell which marketing efforts are working?

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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 identifies sessions where the traffic medium is listed as (not set) in GA4. The medium is one of the most fundamental dimensions for attribution—it helps you categorize traffic into core buckets like organic, email, cpc, or referral.

When medium is (not set):

  • Attribution fails
  • Channels are misclassified
  • Session source/medium reporting becomes unreliable
  • Funnel analysis, campaign ROI, and performance breakdowns are compromised

Common causes include:

  • Broken or missing UTM parameters
  • Clicks from improperly tagged emails, social links, or paid campaigns
  • Auto-tagging failures (especially with Microsoft Ads or Meta if parameters are stripped)
  • Internal redirects stripping parameters before the GA4 tag fires

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How to Conduct This Test

Basic Tests

  • In GA4 > Explore, build a Free-form report:
    • Dimensions: Session source/medium
    • Metrics: Sessions, Conversions, or Revenue
    • Filter for Session medium = (not set)
    • Add a secondary dimension such as Session source, Landing page, or Device category to identify patterns

Advanced QA

  • In BigQuery, run the below query:
    SELECT session_source, session_medium, COUNT(*) AS sessions
    FROM `your_dataset.events_*`
    WHERE session_medium IS NULL OR session_medium = '(not set)'
    GROUP BY session_source, session_medium
    ORDER BY sessions DESC;
  • If you see meaningful session volume under (not set) for medium, your attribution framework is leaking data.

Automated, Free Audit

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How To Fix

  • Ensure all paid and owned links include full UTM parameters:
    • utm_source, utm_medium, and utm_campaign should all be set
  • Use auto-tagging where available (Google Ads, Microsoft Ads), and confirm that UTM parameters or click IDs are preserved on landing pages
  • If using redirects (e.g., vanity URLs, tracking links), ensure they don’t strip UTM parameters
  • Standardize UTM tagging practices across teams and platforms using templates or a URL builder
  • For email, social, and affiliate campaigns, require UTMs at the point of link creation
  • Hire a pro to audit and systematize your campaign tagging so you never lose attribution due to (not set) again.

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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