Fix utm_medium Case Errors in 10 Minutes (Complete Guide)

Problem: Your paid campaigns use utm_medium=CPC (uppercase) instead of utm_medium=cpc (lowercase). Result: 78% of your paid traffic shows as "Unassigned" in GA4.

Solution: 10-minute fix to lowercase all medium values and restore proper channel assignment.

Outcome: Clean channel reporting, accurate ROI, proper attribution.

Let's fix this right now.

The 10-Minute Fix (Step-by-Step)

Step 1: Identify Uppercase Medium Values (2 min)

GA4 � Explore � Free Form

1. Dimension: Session medium
2. Metrics: Sessions
3. Filter: Session default channel group = "Unassigned"
4. Export to CSV

Look for:

• CPC, PPC (should be cpc, ppc)
• EMAIL, Email (should be email)
• SOCIAL, Social (should be social)
• DISPLAY, Display (should be display)

Example output:

Step 2: Fix Platform-by-Platform (6 min)

For each platform, update utm_medium to lowercase:

Google Ads (2 min)

1. Campaigns � Settings
2. Campaign URL options � Tracking template
3. Find: utm_medium=CPC
4. Replace: utm_medium=cpc
5. Save

Or use URL suffix:

utm_source=google&utm_medium=cpc&utm_campaign={{_campaign}}

Facebook Ads (1 min)

1. Ad Manager � All Tools � URL Parameters
2. Edit default parameters
3. Change: utm_medium=CPC � utm_medium=cpc
4. Apply to all campaigns

Email Platform (1 min)

Mailchimp:

1. Campaigns � Templates � Edit
2. Find: utm_medium=Email or utm_medium=EMAIL
3. Replace: utm_medium=email
4. Save as default template

HubSpot:

1. Marketing � Email � Templates
2. Edit tracking settings
3. Change medium to lowercase

LinkedIn Ads (1 min)

1. Campaign Manager � Campaign settings
2. Website � URL tracking parameters
3. Update: utm_medium=cpc (lowercase)

Other Platforms (1 min)

• Twitter Ads: Update destination URL parameters
• Microsoft Ads: Edit tracking template
• TikTok Ads: Update URL parameters

Step 3: Update URL Builder Templates (1 min)

Google Sheets UTM builder:

Add LOWER() function to utm_medium cell:

=LOWER(B2)  // Converts any input to lowercase

Or use data validation dropdown:

List of items: cpc,email,social,display,affiliate,referral

Prevents uppercase from being entered.

Step 4: Verify Fix in GA4 (1 min + 24-48 hours)

Immediate test (GA4 Realtime):

1. Click a link with new lowercase medium
2. GA4 � Realtime
3. Verify traffic appears in correct channel (not Unassigned)

Full verification (24-48 hours):

1. GA4 � Traffic acquisition
2. Check:
   • Unassigned traffic decreased
   • Paid Search sessions increased
   • Email sessions increased
3. Compare with ad platform data to verify alignment

Platform-Specific Fix Instructions

Fix Google Ads URL Parameters

Method 1: Tracking Template (Recommended)

1. Google Ads � Settings � Account settings
2. Tracking � Tracking template
3. Enter:

`{"{"}{"{"}lpurl{"}"}{"}"}}`?utm_source=google&utm_medium=cpc&utm_campaign={{_campaign}}&utm_content={{_ad}}

Applies to all campaigns automatically.

Method 2: Campaign-Level

1. Select campaign � Settings
2. Campaign URL options � Final URL suffix
3. Enter:

utm_source=google&utm_medium=cpc&utm_campaign=`{"{"}{"{"}campaignid{"}"}{"}"}}`

Fix Facebook/Meta Ads

Ad Manager:

1. All Tools � URL Parameters
2. Build URL parameter:
   • Parameter: utm_medium
   • Value: cpc (lowercase)
3. Apply to: All campaigns or selected campaigns

For existing campaigns:

1. Select campaigns � Bulk edit
2. URL parameters � Edit
3. Update utm_medium to lowercase

Fix Email Platforms

Mailchimp:

1. Audience � Settings � Campaign defaults
2. Tracking � Google Analytics link tracking
3. Change utm_medium to: email

SendGrid:

1. Settings � Tracking � Google Analytics
2. Update utm_medium: email

ActiveCampaign:

1. Settings � Tracking � Google Analytics
2. Edit medium: email

Fix Social Media Schedulers

Buffer:

1. Settings � Link Shortening � UTM Tracking
2. Medium: social (lowercase)

Hootsuite:

1. Settings � Social Networks � Tracking
2. Update medium field to: social

Common Fix Mistakes

Mistake 1: Only Fixing Some Platforms

Problem: You fix Google Ads but forget Facebook, email, display.

Result: Partial improvement, still have Unassigned traffic.

Solution: Fix ALL platforms in one session.

Mistake 2: Fixing Templates but Not Active Campaigns

Problem: You update email template but scheduled campaigns still use old version.

Result: Old uppercase values keep generating Unassigned traffic.

Solution: Update active/scheduled campaigns too.

Mistake 3: Not Enforcing Lowercase Going Forward

Problem: You fix current campaigns but team creates new ones with uppercase.

Result: Problem returns next month.

Solution: Lock URL builder to lowercase-only values.

Quick Reference: Case-Sensitive Mediums

Rule: Always lowercase, no exceptions.

Automation: Prevent Future Case Issues

Method 1: Google Sheets Formula

Auto-lowercase any input:

Column C (utm_medium):
=LOWER(B2)

Even if someone types "CPC", formula outputs "cpc".

Method 2: Data Validation Dropdown

Only allow approved lowercase values:

Data � Data validation � List of items:
cpc,email,social,display,affiliate,referral,sms

Impossible to enter uppercase.

Method 3: JavaScript Validation

Website URL builder:

function generateUTM() {
  const medium = document.getElementById('medium').value;
  if (medium !== medium.toLowerCase()) {
    alert('utm_medium must be lowercase');
    return false;
  }
  // Generate URL...
}

Method 4: Pre-Launch Checklist

Before any campaign goes live:

• utm_medium is lowercase
• Test URL in GA4 Realtime
• Verify traffic assigned to correct channel
• Not appearing in "Unassigned"

Historical Data: What About Old Campaigns?

Q: Will fixing case restore historical data? A: No. Historical data remains "Unassigned." Only new traffic (post-fix) gets correct channel assignment.

Workarounds for historical analysis:

Option 1: Manual Consolidation

Export GA4 data to Google Sheets:

1. Download Traffic Acquisition data
2. Add column: "Clean Medium" = LOWER(Medium)
3. Pivot table on "Clean Medium"
4. Now you can see historical performance by corrected medium

Option 2: Set Analysis Cutoff Date

"Analyzing data from [fix date] onward due to UTM parameter correction"

Option 3: Accept and Move Forward

Most teams choose this. Historical data stays broken, but all future data is clean.

FAQ

Do I need to delete old campaigns and start fresh?

No. Just update the tracking parameters in existing campaigns. Most platforms allow editing URL parameters without pausing/recreating campaigns.

Will changing utm_medium affect ad delivery?

Google Ads: May require ad re-approval (usually quick) Facebook: No impact on delivery LinkedIn: No impact

Best practice: Make changes during low-traffic periods (weekends, late evenings).

Can I use title case (Cpc) instead of lowercase?

No. GA4's regex patterns expect all-lowercase. "Cpc" won't match and will create Unassigned traffic.

What if my ad platform auto-capitalizes?

Most platforms don't auto-capitalize URL parameters. If yours does, you can usually override it by manually entering lowercase values in the tracking template.

How do I bulk-update hundreds of campaigns?

Google Ads Editor: Download campaigns, find/replace utm_medium=CPC � utm_medium=cpc, upload

Facebook Ads: Bulk edit tool (select all campaigns, edit URL parameters)

Spreadsheet method: Export campaign list, update in Sheets, reimport

Should I pause campaigns while fixing?

Not necessary. You can edit URL parameters on active campaigns. They'll continue running with new lowercase parameters.