GA4 Channel Grouping Logic: How Source-Medium Determines Channels

David Park's LinkedIn campaign had perfect UTM parameters:

utm_source=linkedin
utm_medium=social
utm_campaign=lead_gen_q4

But when he checked GA4, the campaign appeared under "Organic Social" instead of "Paid Social".

He spent $43,000 on paid ads that GA4 classified as free organic traffic. His boss thought the organic strategy was crushing it. David's paid campaigns looked like they failed.

The problem? David didn't understand how GA4's channel grouping logic actually works. One parameter wrong, and your entire attribution breaks.

How GA4 Channel Grouping Works

GA4 uses a rule-based system to assign traffic to channels.

The Logic Flow

For each session, GA4:

1. Checks the source and medium (from UTM parameters or automatic detection)
2. Runs through channel rules in order (first match wins)
3. Assigns session to the matching channel
4. If no match → Assigns to "Unassigned" channel

The Rule Hierarchy

GA4 evaluates rules in this order:

1. Paid Shopping
2. Paid Search
3. Paid Social
4. Paid Video
5. Display
6. Paid Other
7. Organic Shopping
8. Organic Social
9. Organic Video
10. Organic Search
11. Email
12. Affiliates
13. Referral
14. Direct
15. Unassigned (if nothing matches)

Important: The FIRST matching rule wins. Order matters.

GA4 Default Channel Grouping Rules

Paid Shopping

Traffic is assigned to Paid Shopping if:

(Campaign matches regex: ^(.*(([^a-df-z]|^)shop|shopping).*)$)
AND
(Source matches regex: ^(google|bing)$)
AND
(Medium matches regex: ^(.*cp.*|ppc|paid.*)$)

In plain English:

• Source is Google or Bing
• Medium contains "cp", "ppc", or "paid"
• Campaign contains "shop" or "shopping"

Example:

utm_source=google&utm_medium=cpc&utm_campaign=shopping_feed
→ Paid Shopping ✅

Paid Search

Traffic is assigned to Paid Search if:

(Source matches regex: ^(google|bing|yahoo|baidu|duckduckgo|yandex)$)
AND
(Medium matches regex: ^(.*cp.*|ppc|paid.*)$)

In plain English:

• Source is a search engine (Google, Bing, Yahoo, etc.)
• Medium contains "cp", "ppc", or "paid"

Examples:

utm_source=google&utm_medium=cpc
→ Paid Search ✅

utm_source=bing&utm_medium=ppc
→ Paid Search ✅

utm_source=google&utm_medium=cpc&utm_campaign=brand
→ Paid Search ✅

Paid Social

Traffic is assigned to Paid Social if:

(Source matches regex for social platforms)
AND
(Medium matches regex: ^(.*cp.*|ppc|paid.*)$)

Recognized social sources:

• facebook
• instagram
• linkedin
• twitter
• tiktok
• pinterest
• reddit
• snapchat
• youtube (sometimes)

Examples:

utm_source=facebook&utm_medium=cpc
→ Paid Social ✅

utm_source=linkedin&utm_medium=paid-social
→ Paid Social ✅

utm_source=twitter&utm_medium=ppc
→ Paid Social ✅

Why David's campaign failed:

utm_source=linkedin&utm_medium=social
→ Organic Social ❌
(Medium doesn't contain "cp", "ppc", or "paid")

Paid Video

Traffic is assigned to Paid Video if:

(Medium matches regex: ^(.*cp.*|ppc|paid.*)$)
AND
(Source matches: youtube OR contains video-related patterns)

Examples:

utm_source=youtube&utm_medium=cpc
→ Paid Video ✅

utm_source=google-youtube&utm_medium=cpc
→ Paid Video ✅

Display

Traffic is assigned to Display if:

(Medium matches regex: ^(display|banner|expandable|interstitial|cpm)$)

Examples:

utm_source=google&utm_medium=display
→ Display ✅

utm_source=taboola&utm_medium=display
→ Display ✅

utm_source=outbrain&utm_medium=banner
→ Display ✅

utm_source=any_source&utm_medium=cpm
→ Display ✅

Organic Shopping

Traffic is assigned to Organic Shopping if:

(Campaign matches regex: ^(.*(([^a-df-z]|^)shop|shopping).*)$)
AND
(Source matches regex: ^(google|bing)$)
AND
(Medium matches regex: ^(organic|referral)$)

Example:

utm_source=google&utm_medium=organic&utm_campaign=shopping_organic
→ Organic Shopping ✅

Organic Social

Traffic is assigned to Organic Social if:

(Source matches social platform pattern)
AND
(Medium matches regex: ^(social|social-network|social-media|sm|social network|social media)$)
OR
(Medium is not set and source is social platform)

Examples:

utm_source=facebook&utm_medium=social
→ Organic Social ✅

utm_source=linkedin&utm_medium=social-network
→ Organic Social ✅

utm_source=twitter&utm_medium=social-media
→ Organic Social ✅

utm_source=instagram (no medium)
→ Organic Social ✅

Why this is confusing for paid campaigns:

utm_source=linkedin&utm_medium=social (PAID campaign)
→ Organic Social ❌ (GA4 doesn't know it's paid!)

Organic Video

Traffic is assigned to Organic Video if:

(Source matches: youtube OR video platforms)
AND
(Medium matches regex for video OR social)

Examples:

utm_source=youtube&utm_medium=video
→ Organic Video ✅

utm_source=youtube&utm_medium=social
→ Organic Social ✅ (social takes precedence)

Organic Search

Traffic is assigned to Organic Search if:

(Source matches search engine)
AND
(Medium matches: organic)
OR
(Medium is not set)

Examples:

utm_source=google&utm_medium=organic
→ Organic Search ✅

utm_source=bing (no medium)
→ Organic Search ✅

utm_source=duckduckgo&utm_medium=organic
→ Organic Search ✅

Note: GA4 automatically assigns organic search traffic. You rarely need manual UTMs for this.

Email

Traffic is assigned to Email if:

(Medium matches: email OR e-mail OR e_mail OR e mail)
OR
(Source matches: email OR e-mail OR e_mail OR e mail)

Examples:

utm_source=mailchimp&utm_medium=email
→ Email ✅

utm_source=sendgrid&utm_medium=e-mail
→ Email ✅

utm_source=email&utm_medium=campaign
→ Email ✅ (but source should be platform name)

Affiliates

Traffic is assigned to Affiliates if:

(Medium matches: affiliate OR affiliates)

Examples:

utm_source=cj-affiliate&utm_medium=affiliate
→ Affiliates ✅

utm_source=shareasale&utm_medium=affiliates
→ Affiliates ✅

utm_source=affiliate-wirecutter&utm_medium=affiliate
→ Affiliates ✅

Referral

Traffic is assigned to Referral if:

(Medium matches: referral OR app OR link)

Examples:

utm_source=partner-techcrunch&utm_medium=referral
→ Referral ✅

utm_source=mobile-app&utm_medium=app
→ Referral ✅

utm_source=partner-blog&utm_medium=link
→ Referral ✅

Auto-assigned referrals:

• Traffic from another website (no UTMs)
• GA4 assigns: source=referrer_domain, medium=referral

Direct

Traffic is assigned to Direct if:

(Source is not set OR source = (direct))
AND
(Medium is not set OR medium = (none))

Examples:

• User types URL directly
• Clicks link from email client (non-tracked)
• Clicks link from PDF, document
• HTTPS → HTTP (referrer stripped in some browsers)

Unassigned

Traffic is assigned to Unassigned if:

None of the above rules match

Common causes:

• Conflicting source-medium pairs
• Custom medium not matching any rules
• Source-medium combination GA4 doesn't recognize

Examples:

utm_source=google&utm_medium=social
→ Unassigned ❌

utm_source=facebook&utm_medium=organic
→ Unassigned ❌

utm_source=mailchimp&utm_medium=cpc
→ Unassigned ❌

How to Work With Channel Grouping

Strategy 1: Use Standard Mediums

Stick to GA4-recognized medium values:

✅ Paid campaigns:

• cpc (cost per click)
• ppc (pay per click)
• paid
• paid-social

✅ Organic campaigns:

• social (for social platforms)
• organic (for search engines, auto-assigned)
• email (for email)
• referral (for referrals)

✅ Display campaigns:

• display
• banner
• cpm

✅ Other:

• affiliate
• video

Strategy 2: Match Source Type to Medium Type

Social platforms:

Paid: utm_source=facebook&utm_medium=cpc
Organic: utm_source=facebook&utm_medium=social

Search engines:

Paid: utm_source=google&utm_medium=cpc
Organic: utm_source=google&utm_medium=organic (auto)

Email platforms:

Always: utm_source=mailchimp&utm_medium=email

Strategy 3: Test Before Launch

Validate channel assignment:

1. Create test link with UTMs
2. Click link yourself
3. Check GA4 Realtime → Traffic sources
4. Verify correct channel appears
5. If Unassigned → Fix parameters

Example validation:

Test: LinkedIn Ad Campaign
 
Link:
https://site.com?utm_source=linkedin&utm_medium=cpc&utm_campaign=test
 
Expected in GA4 Realtime:
- Source: linkedin
- Medium: cpc
- Channel: Paid Social ✅
 
If shows:
- Channel: Unassigned ❌
→ Fix medium parameter

Strategy 4: Create Custom Channel Groupings

If GA4's defaults don't match your needs:

1. GA4 → Admin → Data Display → Channel Groups
2. Create new channel grouping
3. Define custom rules
4. Apply to reports

Example custom grouping:

Channel: Brand Social
Rules:
- Source matches: facebook|linkedin|twitter|instagram
- Campaign contains: brand

Channel: Performance Social
Rules:
- Source matches: facebook|linkedin|twitter|instagram
- Campaign contains: performance|conversion

Common Channel Assignment Mistakes

Mistake 1: LinkedIn Paid as Organic

Setup:

utm_source=linkedin&utm_medium=social

Result: Organic Social (wrong for paid campaigns)

Fix:

utm_source=linkedin&utm_medium=cpc

Result: Paid Social ✅

Mistake 2: Google YouTube as Unassigned

Setup:

utm_source=google&utm_medium=social

Result: Unassigned (Google ≠ social)

Fix:

utm_source=google-youtube&utm_medium=cpc

Result: Paid Video ✅

Mistake 3: Email as Referral

Setup:

utm_source=mailchimp&utm_medium=referral

Result: Referral (wrong channel)

Fix:

utm_source=mailchimp&utm_medium=email

Result: Email ✅

Mistake 4: Partner as Email

Setup:

utm_source=partner-techcrunch&utm_medium=email

Result: Email (wrong channel)

Fix:

utm_source=partner-techcrunch&utm_medium=referral

Result: Referral ✅

Mistake 5: Social Organic as Search

Setup:

utm_source=facebook&utm_medium=organic

Result: Unassigned (organic is for search, not social)

Fix:

utm_source=facebook&utm_medium=social

Result: Organic Social ✅

FAQ

Why does my traffic show as "Unassigned"?

Most common causes:

1. Conflicting source-medium pair (e.g., google + social)
2. Custom medium GA4 doesn't recognize
3. Typo in source or medium
4. Wrong platform type (e.g., email platform with social medium)

Solution: Review source-medium combination against GA4 rules above.

Can I change GA4's channel grouping rules?

You can't change the Default channel grouping, but you can:

1. Create custom channel grouping with your own rules
2. Use it in reports instead of default
3. Set as default for your property

How:

• GA4 → Admin → Data Display → Channel Groups
• Create new grouping
• Define custom rules

How do I test which channel my UTMs will assign to?

Method 1: Real-time test

1. Create link with UTMs
2. Click it
3. GA4 → Realtime → Traffic sources
4. Check channel assignment

Method 2: GA4 channel rules

• Review rules in this article
• Match your source-medium to rules manually

What if I use a social source but want it in a different channel?

You can't override default grouping for standard sources.

Options:

1. Use different source name:

   CodeCopy

   Instead of: utm_source=facebook
   Use: utm_source=facebook-custom
   

2. Create custom channel grouping with your own rules

3. Use utm_campaign to differentiate in reports (keeps default channel)

Does capitalization matter for source and medium?

GA4 is case-sensitive.

utm_source=Facebook ≠ utm_source=facebook (two different sources)
utm_medium=CPC ≠ utm_medium=cpc (two different mediums)

Best practice: Always use lowercase to prevent duplicates.

What happens if I don't set a medium?

GA4 assigns channels based on source alone:

• Social platform source → Organic Social
• Search engine source → Organic Search
• Unknown source → Direct or Referral

Best practice: Always set both source and medium for clarity.

Can I see the exact channel rules GA4 uses?

Yes:

1. GA4 → Admin → Data Display → Channel Groups
2. Click "Default channel grouping"
3. View all rules

Or: Use the rules documented in this article (comprehensive).

Related: Conflicting Channel Medium Attribution Rule