What This Rule Detects

GA4 uses specific utm_medium patterns to automatically classify traffic into Default Channel Groups (Paid Search, Email, Organic Social, etc.). When your utm_medium doesn't match these recognized patterns, GA4 classifies ALL traffic as "Unassigned", making channel analysis impossible.

Why It Matters

Business Impact:

• 100% channel visibility loss - Traffic appears in reports but has no channel classification
• Channel comparison impossible - Cannot compare email vs paid vs social performance
• Budget allocation fails - No data to decide where to invest marketing spend
• Executive reporting breaks - Cannot show ROI by channel to stakeholders

Technical Impact:

• GA4's regex pattern matching fails on non-standard medium values
• Traffic appears in "Unassigned" channel group instead of proper channel
• Custom channel grouping required to classify this traffic
• Historical data remains Unassigned even after fixing

Real Example:

• Campaign: Newsletter with utm_medium=newsletter
• GA4 Result: 10,000 sessions classified as "Unassigned"
• Impact: Email channel shows 0 sessions despite active campaigns
• Fix: Change to utm_medium=email → 10,000 sessions now in Email channel

Common Scenarios

Scenario 1: Email Campaign with "newsletter" Medium

Email platforms sometimes suggest utm_medium=newsletter instead of email:

Scenario 2: Social Posts with "boosted_post" Medium

Facebook/Instagram boosted posts using non-standard medium:

Scenario 3: Link Sharing with "pdf" Medium

Content downloads tagged with descriptive but non-standard medium:

How to Fix

Step 1: Identify GA4-Recognized Medium Values

GA4 Default Channel Grouping recognizes these utm_medium patterns:

Paid Search Channel:

• cpc, ppc, paidsearch
• Any medium matching regex: ^(.*cp.*|ppc|paidsearch)$

Organic Search Channel:

• organic
• (Plus automatically detected search engine referrers)

Email Channel:

• email
• Exact match required

Organic Social Channel:

• social, social-network, social-media, sm, social network, social media
• Any medium matching regex: ^(social|social-network|social-media|sm|social network|social media)$

Paid Social Channel:

• Requires medium from Paid Search patterns (cpc, ppc, paidsearch)
• PLUS source from social platforms (facebook, instagram, twitter, linkedin, pinterest, tiktok)

Display Channel:

• display, banner, expandable, interstitial, cpm
• Any medium matching regex: ^(display|cpm|banner)$

Referral Channel:

• referral
• Exact match required

Affiliate Channel:

• affiliate
• Exact match required

Video Channel:

• video
• Exact match required

Step 2: Change utm_medium to Recognized Value

Email Campaigns:

Current: utm_medium=newsletter, email-blast, mailer, e-newsletter
Change to: utm_medium=email

Social Media (Organic):

Current: utm_medium=post, tweet, share, instagram-story
Change to: utm_medium=social

Social Media (Paid):

Current: utm_medium=paid-social, sponsored, promoted-post
Change to: utm_medium=cpc
(Combined with social source, becomes Paid Social channel)

Partner Links:

Current: utm_medium=partner, link, external
Change to: utm_medium=referral

Display Advertising:

Current: utm_medium=banner-ad, graphic-ad, ad-network
Change to: utm_medium=display

Affiliate Marketing:

Current: utm_medium=aff, partner-program, commission
Change to: utm_medium=affiliate

Step 3: Update All Active Campaigns

1. Audit current campaigns - Find all URLs with non-standard mediums
2. Update at the source:
   • Email platform URL templates
   • Social media scheduling tools
   • Ad platform tracking templates
   • Partner/affiliate link generators
3. Test before deploying - Click test link, verify GA4 channel classification in Real-Time reports
4. Document naming convention - Ensure team uses only GA4-recognized values

Step 4: Verify in GA4

1. GA4 → Reports → Acquisition → Traffic acquisition
2. Look for "Unassigned" channel
3. Click into Unassigned → Check utm_medium values
4. After fixing: Sessions should move from Unassigned to proper channels
5. Monitor for 48 hours to confirm all traffic properly classified

Examples

❌ Incorrect Examples

?utm_source=mailchimp&utm_medium=newsletter&utm_campaign=weekly
Result: Unassigned channel (medium="newsletter" not recognized)
Impact: Email campaign invisible in channel reports

?utm_source=facebook&utm_medium=promoted&utm_campaign=spring-sale
Result: Unassigned channel (medium="promoted" not recognized)
Impact: Paid social traffic has no channel classification

?utm_source=partner-site&utm_medium=link&utm_campaign=partnership
Result: Unassigned channel (medium="link" not recognized)
Impact: Referral traffic unclassified

✅ Correct Examples

?utm_source=mailchimp&utm_medium=email&utm_campaign=weekly
Result: Email channel (medium="email" recognized)
Classification: SUCCESS - appears in Email channel reports

?utm_source=facebook&utm_medium=cpc&utm_campaign=spring-sale
Result: Paid Social channel (cpc + facebook source)
Classification: SUCCESS - properly grouped with other paid social

?utm_source=partner-site&utm_medium=referral&utm_campaign=partnership
Result: Referral channel (medium="referral" recognized)
Classification: SUCCESS - traffic correctly classified

GA4 Impact Analysis

Channel Grouping:

• Non-standard mediums → 100% Unassigned channel
• Cannot analyze channel performance trends
• Channel comparison reports show incomplete data
• Default Channel Group visualization missing this traffic

Attribution Models:

• Unassigned traffic excluded from channel-based attribution
• Multi-channel funnels cannot categorize these touchpoints
• Conversion paths show gaps where Unassigned traffic exists
• Cross-channel analysis incomplete

Reporting:

• Channel reports: Traffic volume present but no channel category
• Acquisition overview: Unassigned traffic skews channel distribution
• Executive dashboards: Cannot show ROI by proper channel
• Custom reports: Require complex filters to classify Unassigned traffic

Data Integrity:

• Historical data: Remains Unassigned even after fixing (permanent)
• Trending: Cannot compare channel performance over time if medium changed
• Segmentation: Unassigned traffic requires manual segment creation
• Exports: CSV/API exports show "(not set)" for channel group

Detection in UTMGuard

UTMGuard automatically detects non-standard utm_medium values by:

1. Scans all utm_medium values in your GA4 session data
2. Validates against GA4 Default Channel Grouping regex patterns
3. Flags sessions with unrecognized medium values
4. Counts affected sessions and revenue impact
5. Reports exact medium values to change and suggested replacements

Audit Report Shows:

• Total sessions with non-standard medium
• List of unrecognized medium values found
• Suggested GA4-recognized replacement for each
• Revenue attributed to Unassigned traffic
• Priority ranking by traffic volume

Example Detection:

Issue: Non-Standard utm_medium Value
Affected Sessions: 12,450
Current Value: "newsletter"
Suggested Fix: "email"
Channel Impact: Traffic currently in Unassigned, should be in Email
Revenue Impact: $45,230 revenue unattributed to proper channel

Related Validation Rules

Frequently Asked Questions

Q: Can I create custom channel groups to classify this traffic?

A: Yes, but it's complex and requires ongoing maintenance. Better to use GA4-recognized medium values so Default Channel Grouping works automatically. Custom groups don't apply retroactively to historical data.

Q: What if my medium value is descriptive like "weekly-newsletter"?

A: GA4 only recognizes exact patterns. "weekly-newsletter" doesn't match "email" pattern, causing Unassigned classification. Use utm_medium=email and move descriptive details to utm_campaign or utm_content.

Q: Will changing utm_medium affect historical data?

A: No. Historical sessions remain Unassigned. The fix only applies to future traffic. Consider adding a GA4 annotation marking when you fixed the issue for accurate trend analysis.

Q: Can I use utm_medium=paid-social for Facebook ads?

A: No. GA4 doesn't recognize "paid-social" pattern. Use utm_medium=cpc (or ppc, paidsearch) combined with utm_source=facebook. GA4 automatically classifies this as Paid Social channel.

Q: What about utm_medium=retargeting or utm_medium=remarketing?

A: Not recognized. Use utm_medium=display for retargeting campaigns. Add utm_content=retargeting if you need to distinguish retargeting from prospecting display ads.

Q: How do I classify influencer marketing traffic?

A: Use utm_medium=social (organic influencer posts) or utm_medium=cpc (paid influencer posts). Add utm_source={influencer-name} and utm_campaign={campaign-name} for tracking.

Q: Can UTMGuard suggest the correct medium value for my campaigns?

A: Yes. UTMGuard analyzes your non-standard medium values and suggests the appropriate GA4-recognized replacement based on your campaign context (email, social, display, referral, etc.).

Q: What if I have 50,000 sessions already tracked with wrong medium?

A: Those 50,000 sessions remain Unassigned forever. Fix the utm_medium immediately to ensure future traffic is classified correctly. Historical misclassification is permanent in GA4.

External Resources

• GA4 Default Channel Grouping Documentation
• GA4 Traffic Acquisition Reports
• Campaign URL Builder (Google)
• GA4 Custom Channel Groups Guide
• UTM Parameter Best Practices

---