How to Fix 'GA4 Medium Unrecognized' Error in 5 Minutes

20% of your traffic is trapped in GA4's "Unassigned" channel.

You need it fixed. Now.

Not next week. Not after reading 15 blog posts. Right now.

This is the 5-minute emergency fix for non-standard utm_medium values breaking your GA4 channel attribution.

The 60-Second Diagnosis

Step 1: GA4 → Reports → Traffic Acquisition

Step 2: Look for "Unassigned" in Session default channel group

Step 3: Note the percentage

• < 5%? Minor cleanup needed
• 5-20%? Medium priority fix
• > 20%? Critical—fix immediately

If you see > 5% Unassigned traffic from marketing campaigns, you have this problem.

What's Happening (30-Second Explanation)

GA4 only recognizes specific utm_medium values:

Recognized:

• email
• cpc / ppc
• paidsocial
• display
• affiliate
• social

Not recognized (common mistakes):

• newsletter (should be email)
• paid-social (should be paidsocial)
• retargeting (should be display)
• partner (should be affiliate)
• Email (uppercase—should be lowercase email)

When GA4 sees a utm_medium value it doesn't recognize, it dumps traffic into "Unassigned."

Your attribution breaks. Your reports show missing channels. You can't measure ROI.

The 5-Minute Fix (Step-by-Step)

Step 1: Identify Broken utm_medium Values (2 minutes)

1. GA4 → Explore → Create Free Form
2. Add dimension: Session manual medium
3. Add dimension: Session default channel group
4. Add metric: Sessions
5. Filter: Session default channel group = "Unassigned"
6. Click "Share" → "Download CSV"

You now have a list of every utm_medium value creating Unassigned traffic.

Example output:

utm_medium          | Channel Group | Sessions
--------------------|---------------|----------
newsletter          | Unassigned    | 3,200
paid-social         | Unassigned    | 2,100
retargeting         | Unassigned    | 890
partner             | Unassigned    | 450
Email               | Unassigned    | 340

Step 2: Map to GA4-Recognized Values (1 minute)

For each broken utm_medium, choose the correct replacement:

Step 3: Update Campaign Links (2 minutes)

For each channel, update your link templates:

Email Campaigns

Platform: Mailchimp

1. Settings → Tracking → Google Analytics
2. Change utm_medium default from newsletter to email
3. Save

Platform: HubSpot

1. Settings → Marketing → Tracking
2. Update default UTM parameters
3. Change utm_medium to email

Platform: ActiveCampaign

1. Settings → Tracking
2. Update utm_medium parameter to email

Manual templates:

• Update all email signature links
• Update all newsletter templates
• Change utm_medium=newsletter to utm_medium=email

Social Media Ads

Facebook Ads:

1. Open Facebook Ads Manager
2. Go to each active campaign → Ads tab
3. Edit destination URLs
4. Change utm_medium=paid-social to utm_medium=paidsocial
5. Save

LinkedIn Ads:

1. Campaign Manager → Campaigns
2. Edit destination URLs
3. Change utm_medium=paid-social to utm_medium=paidsocial

Social media scheduler (Hootsuite/Buffer):

1. Settings → Analytics/Tracking
2. Update default utm_medium to paidsocial (for paid posts)
3. Save template

Display & Retargeting Campaigns

Google Display Network:

1. Google Ads → Display campaigns
2. Update tracking template or destination URLs
3. Change utm_medium=retargeting to utm_medium=display

Retargeting platforms:

1. Update URL parameters in platform settings
2. Change to utm_medium=display

Affiliate Links

Affiliate platform templates:

1. Update default utm_medium to affiliate
2. Send updated link format to partners

Manual affiliate links:

• Find all partner links with utm_medium=partner
• Replace with utm_medium=affiliate

Step 4: Verify Fix (Check 24-48 Hours Later)

1. GA4 → Reports → Traffic Acquisition
2. Check "Session default channel group"
3. "Unassigned" should drop 50-90%
4. Email, Paid Social, Display channels should now show traffic

Expected results:

Before fix:

Channel          | Sessions
-----------------|----------
Unassigned       | 8,400 (35%)
Paid Search      | 6,200
Direct           | 5,100
Organic Search   | 4,300

After fix (48 hours later):

Channel          | Sessions
-----------------|----------
Email            | 4,100 (was in Unassigned)
Paid Social      | 2,800 (was in Unassigned)
Paid Search      | 6,200
Direct           | 5,100
Organic Search   | 4,300
Display          | 890 (was in Unassigned)
Affiliate        | 450 (was in Unassigned)
Unassigned       | 460 (was 8,400)

Emergency Lookup Table: Quick Replacements

Use this table for instant utm_medium fixes:

Email

Paid Social

Display Ads

Affiliates

Paid Search

Common Mistakes to Avoid

Mistake 1: Mixing Old and New Values

Wrong:

• Some campaigns use newsletter
• Other campaigns use email

Result: Data split between "Email" channel and "Unassigned."

Right: Update ALL campaigns to email immediately. Don't leave mixed values.

Mistake 2: Using Uppercase

Wrong: utm_medium=Email

Result: Still goes to "Unassigned" (case-sensitive regex)

Right: utm_medium=email (always lowercase)

Mistake 3: Adding Hyphens

Wrong: utm_medium=paid-social

Result: May not match GA4 pattern (depends on version)

Right: utm_medium=paidsocial (no hyphen)

Mistake 4: Platform Names in utm_medium

Wrong:

utm_source=spring-sale&utm_medium=facebook

Result: "facebook" not recognized as utm_medium

Right:

utm_source=facebook&utm_medium=paidsocial

Platform name goes in utm_source. Channel type goes in utm_medium.

Mistake 5: Not Updating Historical Links

Problem: You fix new campaigns, but old email templates still use utm_medium=newsletter.

Result: New traffic goes to "Email" channel. Old template traffic still goes to "Unassigned."

Solution: Update ALL templates, not just new campaigns.

What If You Can't Change utm_medium? (Alternative Fix)

In rare cases, you might not be able to change utm_medium values (e.g., third-party platform limitation).

Alternative solution: Create a custom channel group in GA4.

Create Custom Channel Group

1. GA4 → Admin → Data Display → Channel Groups
2. Click "Create custom channel group"
3. Name it: "Fixed Channel Grouping"
4. Add rules for your non-standard values:

Example custom rules:

Channel: Email
Conditions:
  - Session manual medium exactly matches "newsletter"
  OR
  - Session manual medium exactly matches "email-promotional"

Channel: Paid Social
Conditions:
  - Session manual medium exactly matches "paid-social"
  OR
  - Session manual medium exactly matches "social-paid"

Channel: Display
Conditions:
  - Session manual medium exactly matches "retargeting"
  OR
  - Session manual medium exactly matches "remarketing"

5. Save custom channel group
6. Use it in reports: Exploration → Dimensions → "Custom channel group"

Limitations:

• Doesn't work in standard GA4 reports (only Explorations)
• Doesn't transfer to Looker Studio automatically
• Every user must manually select custom channel group
• Must be recreated for every GA4 property

We recommend fixing utm_medium values instead of creating custom channel groups.

How to Prevent This Problem Forever

1. Create utm_medium Reference Guide

Approved utm_medium values ONLY:

• email - All email campaigns
• cpc or ppc - Paid search
• paidsocial - Paid social ads
• social - Organic social posts
• display - Display ads, retargeting
• affiliate - Affiliate and partner links
• sms - SMS campaigns

Share this with your team. Pin it. Enforce it.

2. Update All Campaign Templates

Don't rely on manual UTM creation.

Set default utm_medium in:

• Email platform settings
• Social media scheduler settings
• URL shortener defaults
• Ad platform tracking templates

3. Validate Before Launch

Before every campaign launch:

1. Create test link with UTM parameters
2. Click it yourself
3. GA4 → Realtime → Check channel classification
4. If "Unassigned" → fix utm_medium before full launch

4. Monthly Spot Check

First Monday of every month:

1. GA4 → Traffic Acquisition
2. Check "Unassigned" %
3. If > 2%, investigate and fix

5. Use UTMGuard

Automate validation with UTMGuard:

• Scans all GA4 traffic
• Detects non-standard utm_medium values
• Alerts you before traffic hits "Unassigned"
• Suggests GA4-recognized replacements

FAQ

How long until GA4 shows the fix?

24-48 hours. GA4 reports update with a delay. Use Realtime reports to verify immediately.

Will fixing utm_medium affect historical data?

No. Historical data stays as-is in "Unassigned." The fix only affects future traffic.

Can I bulk-update old data?

No. GA4 doesn't allow retroactive data changes. Focus on fixing future campaigns.

What if I have 50+ campaign links to update?

Prioritize by traffic volume:

1. Fix the utm_medium values causing MOST Unassigned sessions first
2. Update templates (prevents new mistakes)
3. Update active campaigns
4. Update archived/paused campaigns last

Does this apply to Universal Analytics too?

Universal Analytics had similar (but not identical) channel grouping rules. If you're still using UA, check for "Unassigned" traffic there too.

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Related: GA4 Medium Unrecognized Rule Documentation