GA4 Attribution Models: Which One Should You Use?

By Emily Redmond, Data Analyst at Emilytics · April 2026

TL;DR: Attribution models determine which touchpoint gets credit for a conversion. Last-click is default but dishonest. Linear or time-decay are more fair. Data-driven is best if you have GA4 360. Choose based on your business and funnel length.

Here's a scenario: A user sees your ad on Google, clicks away. Three days later, they come back organically, then buy. Who gets credit—the ad, or organic? GA4's attribution model decides. Pick the wrong one, and your entire budget allocation is wrong.

The Problem with Attribution

Every conversion has a journey. Example:

1. Day 1: User sees retargeting ad (click)
2. Day 2: User returns via organic search
3. Day 3: User clicks email campaign link
4. Day 3: User makes purchase

Last-click attribution: Email gets 100% credit (it was the last touchpoint before conversion).

First-click attribution: Retargeting ad gets 100% credit (it first introduced the user).

Linear attribution: Each touchpoint gets 33% credit.

Reality: All three touchpoints contributed to the conversion. None deserves 100% and none deserves 0%.

GA4's Attribution Models Explained

1. Last-Click Attribution

How it works: The last touchpoint before conversion gets 100% credit.

Example: User sees display ad → searches organic → purchases. Organic gets 100% credit.

Pros:

• Simple to understand
• Good for understanding immediate drivers of conversion

Cons:

• Ignores the journey
• Overstates the value of channels near the end of the funnel (retargeting, brand search)
• Understates the value of awareness channels (content, display)
• Encourages over-investment in last-click channels

When to use: Never, ideally. But this is the industry default because it's simple.

💡 Emily's take: I've seen teams spend millions on retargeting because last-click attribution made it look like the best-performing channel. But retargeting wouldn't work without awareness channels creating the initial interest. Last-click lies.

2. First-Click Attribution

How it works: The first touchpoint gets 100% credit.

Example: User sees display ad → searches organic → purchases. Display gets 100% credit.

Pros:

• Shows which channels create awareness
• Good for understanding top-of-funnel performance

Cons:

• Ignores the journey
• Overstates awareness channels
• Understates the value of conversion channels
• Encourages over-investment in brand awareness

When to use: Use alongside other models to understand top-of-funnel value. Not alone.

3. Linear Attribution

How it works: All touchpoints get equal credit.

Example: User sees display ad → searches organic → purchases. Each gets 33% credit.

Pros:

• Fair (all touchpoints get equal weight)
• Shows the whole journey

Cons:

• Ignores that different touchpoints have different impact
• Doesn't account for time decay (early touchpoints might matter less)

When to use: When you have a simple, short funnel. Good for starting point if you don't have GA4 360.

4. Time-Decay Attribution

How it works: Touchpoints closer to conversion get more credit.

Example: User sees display ad (day 1) → searches organic (day 2) → purchases (day 3).

• Display ad: 25% credit
• Organic: 75% credit

(The exact weights depend on GA4's half-life, typically 7 days by default.)

Pros:

• Acknowledges that recent touchpoints matter more
• Balances awareness and conversion
• More realistic than linear

Cons:

• Arbitrary weighting (why 7-day half-life? Why not 5 days?)
• Still not as good as data-driven

When to use: Good compromise if you don't have GA4 360. Fair to most channels.

5. Data-Driven Attribution (GA4 360 Only)

How it works: Google's machine learning analyzes your conversion data to determine which touchpoints actually drive conversions.

Example: Google sees that users who see display ads convert at 5%, but users who see display ads AND then do organic search convert at 20%. It adjusts credit accordingly.

Pros:

• Most accurate (based on your actual data)
• Unbiased (no human assumptions)
• Shows true channel value

Cons:

• GA4 360 only (~$150k+/year)
• Requires lots of conversion data (GA4 360 typically recommends 1,000+ conversions/month)

When to use: If you have GA4 360 and enough conversion volume. This is the gold standard.

Comparing Models Side-by-Side

Notice how each model tells a different story. Last-click says email is everything. First-click says display is everything. Data-driven says organic is most important (because it correlates with conversions in your specific data).

Choosing a Model for Your Business

For Ecommerce

Use time-decay or data-driven.

Reasoning: Ecommerce has a shorter, clearer funnel. Recent touchpoints (retargeting, final search) matter more. But awareness channels still matter. Data-driven is best if you have volume.

For SaaS / B2B

Use time-decay or data-driven.

Reasoning: Enterprise sales have longer, complex journeys. Many touchpoints contribute. Data-driven is ideal if you have it.

For Content / Publishers

Use linear or time-decay.

Reasoning: Multiple content pieces and referral sources contribute. Linear is honest; time-decay acknowledges that recent content matters more.

For Lead Generation

Use linear or first-click.

Reasoning: The first touchpoint (which ad/channel) often determines lead quality. Linear gives balance.

How to Change Your Attribution Model in GA4

1. Go to Admin → Reporting identity
   • Or Admin → Conversion settings (depending on GA4 version)
2. Look for "Attribution model"
3. Change from "Last-click" to your preferred model
4. Save

GA4 will re-calculate your conversion attribution. It takes a few hours to process.

Important: This affects how conversions are attributed going forward. It doesn't change historical data retroactively. You can still view old data under the old model if you view reports before making the change.

Viewing Conversions Under Different Models

In Explorations, you can compare attribution models side-by-side:

1. Create a Freeform exploration
2. Dimension: Campaign
3. Metrics: Conversions
4. Segment comparison: Add one segment per attribution model
5. Compare

This shows which model paints the most useful picture for your business.

Best Practices

1. Test multiple models: Don't just pick one. Compare first-click, linear, and time-decay. See which tells a story that makes sense.

2. Match your funnel: Longer funnels (SaaS) → time-decay or data-driven. Shorter funnels (ecommerce) → linear or time-decay.

3. Monitor channel performance: With your chosen model, track which channels drive the most attributed conversions. Allocate budget accordingly.

4. Plan for GA4 360: If you have volume, upgrade to GA4 360 for data-driven attribution. It's worth the investment for accurate budgeting.

5. Combine with cost data: With attribution model + cost data, calculate true ROI per channel. This is the most actionable metric.

Common Misconceptions

"Last-click is the most accurate." Wrong. It's the simplest, but accuracy requires acknowledging that multiple touchpoints contribute.

"Linear is always fair." Not necessarily. Linear treats day-1 touchpoints the same as day-7 touchpoints, even though recency matters.

"I can only use one model." False. GA4 lets you view conversions under different models. Use multiple for different questions.

"Attribution doesn't matter if I'm tracking everything." Wrong. How you allocate credit determines your budget decisions. The wrong model leads to budget misallocation.

Frequently Asked Questions

Q: Which model does GA4 use by default? A: Last-click. But you should change it.

Q: Can I change my attribution model retroactively for old data? A: No. GA4 only re-calculates going forward. To compare old data, view it under the old model before changing.

Q: Does changing attribution model affect my Google Ads optimization? A: Google Ads has its own attribution settings (separate from GA4). Changing GA4 doesn't affect Ads optimization directly.

Q: What if I have multiple conversion types? A: Each conversion type can have its own attribution model. A purchase might use time-decay; a sign-up might use linear.

Q: Can I use different attribution models in different reports? A: Not in standard reports (each report uses your default model). But you can build different explorations comparing models.

The Bottom Line

Attribution is broken in most organizations. Last-click lies. But fixing it is simple: choose a model that reflects your business (time-decay for most), then budget based on truth.

If you have volume, get GA4 360 for data-driven attribution. It's the only truly honest model.

For combining attribution with cost data to calculate ROI, see How to Import Cost Data Into GA4.

Emily Redmond is a data analyst at Emilytics — the AI analytics agent that watches your GA4, Search Console, and Bing data around the clock so you never miss what matters. 8 years of experience helping founders and growth teams turn data noise into clear decisions. Say hi →