GA4 Lowercase UTM Requirements: Complete Reference Guide

GA4's Default Channel Grouping has ONE non-negotiable requirement: utm_medium must be lowercase.

Not "mostly lowercase." Not "lowercase when you remember." Always lowercase.

Here's the complete reference guide for every GA4-recognized utm_medium value, why lowercase matters, and how to enforce it across your organization.

Complete GA4 utm_medium Reference

Paid Search / PPC

Required format: Lowercase

Regex pattern: ^(cpc|ppc|paidsearch).*$

Examples that work:

• utm_medium=cpc
• utm_medium=ppc
• utm_medium=cpc-brand (starts with cpc)

Examples that fail:

• utm_medium=CPC → Unassigned
• utm_medium=paid-search → Unassigned (hyphen breaks pattern)

Email

Required format: Exact match, lowercase

Regex pattern: ^(email|e-mail|e_mail|e mail)$

Note: Must match exactly (no suffixes like "email-promo").

Social

Required format: Contains "social" (lowercase)

Regex pattern: Contains social|social-network|social-media|sm|social network|social media

Display

Required format: Starts with display/cpm/banner (lowercase)

Regex pattern: ^(display|cpm|banner).*$

Affiliates

Required format: Starts with "affiliate" (lowercase)

Regex pattern: ^(affiliate|affiliates).*$

Referral

Required format: Starts with "referral" (lowercase)

Regex pattern: ^referral$

Video/Audio/SMS (Additional Channels)

Why Lowercase is Required

Reason 1: Regex is Case-Sensitive

GA4 channel grouping uses regex patterns that match exact character case.

Pattern: ^cpc$ Matches: cpc Does NOT match: CPC, Cpc, cPc

There's no "fuzzy matching" or "close enough." Either it matches or it doesn't.

Reason 2: Consistency Across Properties

Google wants standardized reporting across all GA4 properties. Requiring lowercase ensures:

• Same UTM structure works everywhere
• Cross-property comparisons are valid
• Documentation applies universally

Reason 3: Technical Limitations

URL parameters are case-sensitive by default in web standards. GA4 doesn't normalize case because:

• Would require processing overhead
• Could cause unintended side effects
• Breaks standardization

Google's decision: Require lowercase, document it, enforce it.

Enforcing Lowercase Standards

Method 1: URL Builder with Auto-Lowercase

Google Sheets formula:

Column: utm_medium
Formula: =LOWER(B2)

Effect: No matter what user types, output is lowercase.

Method 2: Dropdown Lists

Data validation:

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

Effect: User can only select pre-approved lowercase values.

Method 3: JavaScript Validation

Website URL builder:

function buildURL() {
  let medium = document.getElementById('medium').value;
  
  // Auto-convert to lowercase
  medium = medium.toLowerCase();
  
  // OR validate and reject uppercase
  if (medium !== medium.toLowerCase()) {
    alert("utm_medium must be lowercase");
    return false;
  }
  
  // Build URL...
}

Method 4: Team Documentation

Create a one-page quick reference:

UTM STANDARDS

utm_medium MUST be lowercase. Always.

✅ CORRECT:
- utm_medium=cpc
- utm_medium=email
- utm_medium=social

❌ WRONG:
- utm_medium=CPC
- utm_medium=Email
- utm_medium=SOCIAL

When in doubt: LOWERCASE.

Testing for Compliance

Pre-Launch Test

Before any campaign goes live:

1. Copy test URL
2. Visit your site using test URL
3. GA4 → Realtime (wait 1-2 minutes)
4. Check: Event with session_start
5. Verify: Session medium shows lowercase value
6. Confirm: Traffic assigned to correct channel (not Unassigned)

Monthly Audit

GA4 → Explore → Free Form:

• Dimension: Session medium
• Metrics: Sessions
• Export to CSV

Check for:

• Any uppercase values (CPC, EMAIL, SOCIAL)
• Mixed case (Cpc, Email)
• Immediately fix active campaigns

Platform-Specific Lowercase Requirements

Google Ads

Tracking template:

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

Note: Lowercase "cpc" is critical.

Facebook Ads

URL parameters:

utm_source=facebook&utm_medium=cpc&utm_campaign={"{"}{"{"}campaign.name{"}"}{"}"}}

Facebook doesn't auto-capitalize if you enter lowercase.

Email Platforms

Most email platforms default to lowercase:

• Mailchimp: utm_medium=email (lowercase default)
• SendGrid: utm_medium=email (lowercase)
• HubSpot: Check settings, may auto-capitalize

Always verify platform doesn't override to title case.

Social Schedulers

Buffer, Hootsuite, Later:

• Check UTM tracking settings
• Ensure medium is set to lowercase
• Test with one post before bulk scheduling

Common Questions

Q: Can I use utm_medium=Cpc (title case)? A: No. Will appear as Unassigned. Must be all lowercase: cpc.

Q: What about utm_medium=CPC_Google (uppercase with suffix)? A: Still fails. Must start with lowercase: cpc_google.

Q: Does uppercase break utm_source too? A: No, but creates data fragmentation (google vs Google appear as 2 sources). Best practice: Lowercase everything.

Q: Can I create custom channel groups to accept uppercase? A: Yes, but workaround. Better to fix utm_medium values to lowercase.

Q: Will GA4 ever support case-insensitive matching? A: No official plans. Google's position: Follow documented lowercase standards.