January 20266 min read

Conversions & Key Events

Set up conversion tracking, understand attribution models, and optimize for business outcomes.

Key Events Overview

In 2024, Google updated terminology to clarify the difference between GA4 and Google Ads:

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Key Events = Conversions in GA4 reports
Conversions = Key Events imported to Google Ads

An event can be BOTH a Key Event AND a Conversion

Why the Change?

| Term | Where It Appears | Purpose | |------|------------------|---------| | Key Event | GA4 interface | Mark important actions for GA4 reporting | | Conversion | Google Ads | Optimize ad bidding, measure campaign ROI |

What Should Be a Key Event?

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High-Value Actions:
├── purchase (revenue)
├── generate_lead (lead form submission)
├── sign_up (account creation)
├── begin_checkout (cart intent)
└── contact_form_submit (inquiry)

Medium-Value Actions:
├── add_to_cart
├── view_item (high-value product)
├── file_download (brochure, whitepaper)
└── video_complete (product demo)

Key Event Limits

| Limit | Amount | |-------|--------| | Key events per property | 30 | | Recommended minimum | 3-5 key events | | Ideal for Google Ads | 1-3 primary conversions |

Setting Up Conversions

Method 1: Mark Existing Event as Key Event

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Admin → Events → Find event → Toggle "Mark as key event"

Method 2: Create Event Then Mark as Key Event

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Step 1: Admin → Events → Create event
Step 2: Set conditions (e.g., page_view where page_location contains "/thank-you")
Step 3: Toggle "Mark as key event"

Method 3: Using Google Tag Manager

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1. Create GA4 Event tag for conversion action
2. Configure trigger (form submit, button click, etc.)
3. Publish tag
4. Wait for event to appear in GA4
5. Mark as key event in GA4 Admin

Conversion Counting Methods

| Method | Description | Best For | |--------|-------------|----------| | Once per event | Count every occurrence | Purchases, downloads | | Once per session | Count max once per session | Lead forms, signups |

Default: GA4 counts conversions "once per event" by default. For lead generation, you may want "once per session" to avoid duplicates.

E-commerce Conversions

For purchase events, ensure you pass value and currency:

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gtag('event', 'purchase', {
  'transaction_id': 'T12345',
  'value': 149.99,  // Required for revenue tracking
  'currency': 'USD', // Required for revenue tracking
  'items': [{
    'item_id': 'SKU123',
    'item_name': 'Product',
    'price': 149.99,
    'quantity': 1
  }]
});

Attribution Models

Attribution determines which marketing touchpoints get credit for conversions.

Available Models

| Model | How It Works | Best For | |-------|--------------|----------| | Data-Driven | ML assigns credit based on impact | Most properties (recommended) | | Last Click | 100% to final touchpoint | Simple attribution | | First Click | 100% to first touchpoint | Understanding discovery | | Linear | Equal credit to all touchpoints | Valuing all interactions | | Time Decay | More credit to recent touchpoints | Short purchase cycles | | Position-Based | 40% first, 40% last, 20% middle | Balanced view |

Data-Driven Attribution (Default)

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How it works:
├── Analyzes ALL conversion paths
├── Uses machine learning
├── Assigns fractional credit
├── Updates continuously
└── Requires sufficient conversion volume

Requirement: Data-driven attribution requires enough conversions to train the model. For low-volume properties, GA4 falls back to last-click.

Changing Attribution Model

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Admin → Data Display → Attribution settings

Options:
├── Reporting attribution model
├── Lookback window
└── Conversion path settings

Model Comparison

Use the Model Comparison tool to see how attribution changes:

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Advertising → Attribution → Model comparison

Compare:
├── Data-driven vs Last click
├── See credit shifts by channel
└── Identify undervalued channels

Conversion Windows

The lookback window determines how far back GA4 looks for touchpoints to credit.

Window Options

| Window Type | Duration Options | Default | |-------------|------------------|---------| | Acquisition conversion | 30 days | 30 days | | Other conversions | 30, 60, or 90 days | 90 days | | Engaged-view | 3 days | 3 days |

Setting Conversion Windows

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Admin → Data Display → Attribution settings → Lookback window

Best Practices

| Business Type | Recommended Window | |---------------|-------------------| | E-commerce (low AOV) | 30 days | | E-commerce (high AOV) | 60-90 days | | B2B / Long sales cycle | 90 days | | Impulse purchases | 30 days |

Modeled Conversions

GA4 uses machine learning to fill gaps when cookies are blocked or consent is denied.

How Modeling Works

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Known Data + ML Models = Estimated Total

When modeling is used:
├── User denied cookie consent
├── iOS users with ATT declined
├── Browser blocked cookies
├── Cross-device gaps
└── Conversion path incomplete

Modeled Conversion Requirements

For GA4 to model conversions:

Sufficient conversion volume
Consent Mode v2 implemented
Enough "consented" data to train models
Property meets minimum thresholds

Consent Mode v2

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// Consent mode implementation
gtag('consent', 'default', {
  'analytics_storage': 'denied',
  'ad_storage': 'denied',
  'wait_for_update': 500
});

// After user consent
gtag('consent', 'update', {
  'analytics_storage': 'granted',
  'ad_storage': 'granted'
});

Viewing Modeled Data

In reports, modeled conversions are blended with observed data. Look for:

"Includes modeled data" indicator
Data quality icons in reports
Attribution reports showing modeling %

Google Ads Integration

Linking Google Ads

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Admin → Product links → Google Ads links → Link

Benefits:
├── Import key events as conversions
├── View Google Ads data in GA4
├── Create audiences for remarketing
└── Enable auto-tagging

Importing Key Events to Google Ads

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In Google Ads:
Tools → Conversions → New conversion action → Import → Google Analytics 4

Select:
├── Which key events to import
├── Primary vs secondary conversion
└── Conversion value settings

Primary vs Secondary Conversions

| Type | Use in Bidding | Reporting | |------|----------------|-----------| | Primary | Yes - optimizes bids | Conversions column | | Secondary | No | All conversions column |

Best Practices

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## For Google Ads Integration

□ Link GA4 to Google Ads immediately
□ Enable auto-tagging in Google Ads
□ Import 1-3 primary conversions max
□ Use "purchase" or "generate_lead" as primary
□ Import others as secondary for insights
□ Align attribution models between platforms
□ Allow 24-48 hours for data to sync

Warning: Don't import too many primary conversions. Smart Bidding works best with 1-3 focused conversion actions with sufficient volume (30-50+ per month).