How UTM Truncation Creates Duplicate Data in GA4

You launch 5 different email campaigns targeting different customer segments.

You check GA4 one week later. You see ONE campaign row with all the traffic merged together.

You can't tell which segment performed best. Which subject line won. Which offer drove conversions.

Five campaigns. One row. All because your campaign names were too long and got truncated to the same 100-character string.

This is UTM truncation creating duplicate data—and it's destroying your ability to measure campaign performance.

How Truncation Creates Duplicates

The mechanism:

1. You create Campaign A: email_2024_january_promo_segment_vip_customers_offer_70_percent_off_subject_free_shipping_creative_variant_a (110 characters)

2. You create Campaign B: email_2024_january_promo_segment_regular_customers_offer_50_percent_off_subject_sale_ends_creative_variant_b (116 characters)

3. Both exceed 100 characters

4. GA4 truncates both to 100 characters:

   • Campaign A → email_2024_january_promo_segment_vip_customers_offer_70_percent_off_subject_free_shipping_creat
   • Campaign B → email_2024_january_promo_segment_regular_customers_offer_50_percent_off_subject_sale_ends_cre

5. If they share a common prefix of 100+ characters: Both become: email_2024_january_promo_segment_vip_customers_offer_70_percent_off_subject_free_shipping_creat

6. GA4 sees ONE campaign name

7. All sessions merge into ONE row

Real Example: 7 Campaigns Became 1 Row

Company: B2B SaaS Campaign: Q1 2024 webinar series

Campaign names:

1. webinar_registration_2024_q1_march_project_management_best_practices_for_remote_teams_targeting_segment_enterprise
2. webinar_registration_2024_q1_march_project_management_best_practices_for_remote_teams_targeting_segment_smb
3. webinar_registration_2024_q1_march_project_management_best_practices_for_remote_teams_targeting_segment_startup
4. webinar_registration_2024_q1_march_project_management_best_practices_for_remote_teams_targeting_segment_agency
5. webinar_registration_2024_q1_march_project_management_best_practices_for_remote_teams_targeting_segment_nonprofit
6. webinar_registration_2024_q1_march_project_management_best_practices_for_remote_teams_targeting_segment_education
7. webinar_registration_2024_q1_march_project_management_best_practices_for_remote_teams_targeting_segment_government

All 7 campaigns: 120-135 characters

GA4 truncated all to 100 characters:

webinar_registration_2024_q1_march_project_management_best_practices_for_remote_teams_targeting_segm

All differentiation (enterprise vs smb vs startup) cut off after character 100.

GA4 report showed:

• ONE campaign: webinar_registration_2024_q1_march_project_management_best_practices_for_remote_teams_targeting_segm
• Total sessions: 2,847
• Conversions: 134

Couldn't answer:

• Which segment converted best?
• Should we focus on enterprise or SMB?
• Which audience had highest registration rate?

$18,000 spent on segmented targeting. Zero ability to measure which segment performed.

Common Truncation Patterns

Pattern 1: Sequential Campaign Numbers

Campaigns:

spring_sale_2024_email_promotional_segment_existing_customers_high_value_campaign_variant_test_number_1
spring_sale_2024_email_promotional_segment_existing_customers_high_value_campaign_variant_test_number_2
spring_sale_2024_email_promotional_segment_existing_customers_high_value_campaign_variant_test_number_3

All truncate to:

spring_sale_2024_email_promotional_segment_existing_customers_high_value_campaign_variant_test_nu

The differentiator ("number_1", "number_2", "number_3") is chopped off.

Result: Three campaigns appear as ONE.

Pattern 2: Date Variations

Campaigns:

newsletter_weekly_digest_promotional_content_featuring_blog_articles_and_product_updates_sent_january_08_2024
newsletter_weekly_digest_promotional_content_featuring_blog_articles_and_product_updates_sent_january_15_2024
newsletter_weekly_digest_promotional_content_featuring_blog_articles_and_product_updates_sent_january_22_2024

All truncate to:

newsletter_weekly_digest_promotional_content_featuring_blog_articles_and_product_updates_sent_jan

The date is cut off. Can't tell which week's newsletter performed better.

Pattern 3: A/B Test Variants

Campaigns:

black_friday_sale_2024_promotional_email_campaign_subject_line_test_get_70_percent_off_everything_variant_a
black_friday_sale_2024_promotional_email_campaign_subject_line_test_get_70_percent_off_everything_variant_b
black_friday_sale_2024_promotional_email_campaign_subject_line_test_get_70_percent_off_everything_variant_c

All truncate to:

black_friday_sale_2024_promotional_email_campaign_subject_line_test_get_70_percent_off_everything_v

Variant indicator (a, b, c) removed. Can't determine winning variant.

How to Detect Merged Campaigns

Method 1: Compare Launch Count vs GA4 Rows

Launched campaigns: 7 GA4 shows: 1 row

Gap = merged campaigns.

Method 2: Session Volume Analysis

GA4 shows:

• Campaign: webinar_reg_2024_... → 2,847 sessions

Your email platform shows:

• 7 campaigns sent
• Average 400 sessions each
• Expected total: ~2,800 sessions

Math checks out, but shouldn't be ONE row—should be 7 rows.

Method 3: Character Count Inspection

Export campaign names from GA4:

Campaign Name | Sessions | Character Count
webinar_registration_2024_q1_march_project_... | 2,847 | 100

If character count = EXACTLY 100 → likely truncated.

Check source campaign names in email/ad platform—are they longer than 100?

Method 4: Check for Ellipsis Pattern

Truncated campaigns often end mid-word:

...remote_teams_targeting_segm   ← Ends at "segm" (truncated from "segment")
...variant_test_nu               ← Ends at "nu" (truncated from "number")
...subject_line_te               ← Ends at "te" (truncated from "test")

These are red flags for truncation.

Impact on Attribution

Problem 1: Can't Identify Winners

A/B test: 3 subject line variants GA4: Shows 1 merged campaign Result: Can't determine winning variant

You optimize future campaigns based on... nothing.

Problem 2: Incorrect ROI Calculation

Campaign A: $2,000 spend, VIP segment (high LTV) Campaign B: $4,000 spend, regular segment (medium LTV)

GA4 merges both:

• Shows $6,000 spend
• Can't separate VIP vs regular performance
• Can't calculate segment-specific ROI

Might conclude: "Email isn't profitable" when reality is VIP segment has 4x ROI but regular segment is breakeven.

Problem 3: Lost Optimization Insights

What you wanted to learn:

• Which customer segment responds best?
• Which offer (70% off vs BOGO) drives more revenue?
• Which creative style performs better?

What you actually learned:

• "This merged campaign got 2,847 sessions"

Zero actionable insights.

Prevention Strategies

Strategy 1: Front-Load Differentiators

Bad (differentiator at end):

email_newsletter_promotional_2024_january_winter_sale_segment_vip
email_newsletter_promotional_2024_january_winter_sale_segment_regular

If truncated, both become:

email_newsletter_promotional_2024_january_winter_sale_segment_vip    ← 62 chars (safe)

Good (differentiator early):

vip_2024_jan_winter_sale_email
regular_2024_jan_winter_sale_email

Even if truncated, differentiation preserved.

Strategy 2: Keep Total Under 85 Characters

Buffer for safety:

• Limit: 100 characters
• Target: 85 characters
• Safety margin: 15 characters

Why 85? Accounts for potential URL encoding expansion (spaces, special chars).

Strategy 3: Use utm_content for Variations

Instead of:

utm_campaign=spring_sale_2024_email_promo_segment_vip_offer_70pct_variant_a

Use:

utm_campaign=spring_sale_2024_vip
utm_content=offer_70pct_variant_a

Benefits:

• Campaign name stays short
• Variations tracked in content
• Can still segment/filter by content

Strategy 4: Standardized Abbreviations

Create team glossary:

• newsletter → nl
• promotional → promo
• campaign → cmpn
• segment → seg
• variant → var
• january → jan, february → feb, etc.

Before:

newsletter_promotional_january_2024_winter_sale_segment_vip (64 chars)

After:

nl_promo_2024_jan_winter_sale_vip (33 chars - saved 31 chars!)

FAQ

Can I retroactively fix merged campaigns in GA4?

No. Once campaigns are merged due to truncation, historical data cannot be separated in GA4. You can only:

1. Correlate with source platform data (email sent dates, ad campaign IDs)
2. Manually track which campaigns launched when
3. Accept the merged data and fix going forward

How do I know if my campaigns are merging?

Compare counts:

• Campaigns launched (from your tracking sheet): 7
• Campaigns in GA4 (Traffic Acquisition): 1

If GA4 count < launch count → merging likely.

What if I need long descriptive names for internal tracking?

Use two naming systems:

GA4 (utm_campaign): Short, under 85 chars

utm_campaign=q1_webinar_pm_2024

Internal tracker (spreadsheet): Full descriptive name

Internal: "Q1 2024 Webinar: Project Management Best Practices for Remote Teams - Enterprise Segment"
UTM: q1_webinar_pm_2024_ent

Maintain lookup table mapping short → long names.

Does truncation affect other analytics platforms?

Varies by platform:

• Adobe Analytics: 255-character limit (more forgiving)
• Matomo: No hard limit (depends on database config)
• Mixpanel: 255-character limit

GA4's 100-character limit is notably strict.

Can I use URL shorteners to avoid truncation?

No—truncation happens at GA4 data collection, not URL length.

URL shorteners shorten the overall URL, but GA4 still extracts and truncates individual UTM parameter values at 100 characters.

What if my platform auto-generates long campaign names?

Override the auto-generation:

• Use custom campaign name field (if available)
• Build URLs externally and paste complete URLs
• Contact platform support to request character limit enforcement