google-analytics

What this skill does

# Google Analytics 4 Complete Guide

## Overview

Google Analytics 4 (GA4) is Google's event-based analytics platform for measuring user interactions across websites and applications. Every user interaction is tracked as an event with associated parameters, providing flexible cross-platform measurement.

## When to Use This Skill

Invoke this skill for any GA4-related task:

- Setting up GA4 properties, data streams, and Measurement IDs
- Installing GA4 via gtag.js, GTM, or CMS plugins
- Implementing event tracking (automatic, recommended, custom, ecommerce)
- Creating custom dimensions, audiences, and reports
- Exporting data to BigQuery for SQL analysis
- Server-side tracking via Measurement Protocol
- User ID and cross-device tracking
- Privacy compliance, Consent Mode, and GDPR/CCPA
- Testing and debugging with DebugView

## Quick Start

1. **Create property:** analytics.google.com -> Admin -> Create -> Property
2. **Create data stream:** Add web stream, note Measurement ID (G-XXXXXXXXXX)
3. **Install tracking** (choose one):
   - **GTM (recommended):** Install container, create Google Tag with Measurement ID, trigger on All Pages, publish
   - **gtag.js direct:**
     ```html
     <script async src="https://www.googletagmanager.com/gtag/js?id=G-XXXXXXXXXX"></script>
     <script>
       window.dataLayer = window.dataLayer || [];
       function gtag(){dataLayer.push(arguments);}
       gtag('js', new Date());
       gtag('config', 'G-XXXXXXXXXX');
     </script>
     ```
4. **Verify:** Enable GA Debugger extension, check Admin -> DebugView for session_start, page_view
5. **Send custom events:**
   ```javascript
   gtag('event', 'button_click', { button_name: 'Subscribe', button_location: 'header' });
   ```

## Decision Tree: Which Reference Do I Need?

```
What are you trying to do?

Setting up GA4 for the first time?         -> references/setup.md
Understanding how events work?              -> references/events-fundamentals.md
Implementing standard tracking events?      -> references/recommended-events.md
Creating business-specific custom events?   -> references/custom-events.md
Making parameters appear in reports?        -> references/custom-dimensions.md
Implementing User ID / cross-device?        -> references/user-tracking.md
Building audiences for remarketing?         -> references/audiences.md
Analysing data in GA4 reports?              -> references/reporting.md
Exporting to BigQuery for SQL analysis?     -> references/bigquery.md
Installing via gtag.js directly?            -> references/gtag.md
Setting up GA4 in Google Tag Manager?       -> references/gtm-integration.md
Sending events from server/backend?         -> references/measurement-protocol.md
Testing and debugging implementation?       -> references/debugview.md
Implementing GDPR/Consent Mode?             -> references/privacy.md
Configuring Admin settings?                 -> references/data-management.md
```

## Core Concepts

### Event-Based Model

GA4 tracks everything as events in four categories:

| Category | Description | Examples |
|----------|-------------|----------|
| Automatic | Fire without configuration | session_start, first_visit |
| Enhanced Measurement | Toggle on/off in settings | scroll, click, file_download |
| Recommended | Google-defined with standard parameters | purchase, login, sign_up |
| Custom | Business-specific tracking | demo_requested, trial_started |

### Key Limits

| Limit | Value |
|-------|-------|
| Event names per property | 500 distinct |
| Parameters per event | 25 |
| Event name length | 40 characters |
| Parameter name/value length | 40 / 100 characters |
| Custom dimensions (event/user/item) | 50 / 25 / 10 |
| Audiences per property | 100 |

### Measurement ID

- Format: `G-XXXXXXXXXX` (G- prefix + 10 alphanumeric characters)
- Location: Admin -> Data Streams -> Web Stream
- Used in: gtag.js config, GTM tags, Measurement Protocol

## Common Workflows

### Ecommerce Tracking

1. Review [recommended events](references/recommended-events.md) for the purchase funnel: view_item -> add_to_cart -> begin_checkout -> purchase
2. Structure items array (required: item_id OR item_name; recommended: price, quantity, item_category)
3. Test with [DebugView](references/debugview.md), then register custom item parameters as [custom dimensions](references/custom-dimensions.md)

### Cross-Device Tracking

1. Implement [User ID](references/user-tracking.md) and configure Reporting Identity (Admin -> Data Settings)
2. Set [user properties](references/custom-dimensions.md) and build [cross-device audiences](references/audiences.md)

### GDPR Compliance

1. Set up [Consent Mode](references/privacy.md) with default denied state
2. Integrate with CMP (OneTrust, Cookiebot, etc.), update consent on user acceptance
3. Test consent implementation with [DebugView](references/debugview.md)

### Custom Reports

1. Understand available data in [reporting](references/reporting.md)
2. Register custom parameters as [dimensions](references/custom-dimensions.md), create Explorations
3. For unsampled data, export to [BigQuery](references/bigquery.md)

## Best Practices

- **Naming:** Use snake_case, be descriptive and action-oriented, keep under 40 characters, avoid generic names
- **Implementation order:** Enhanced Measurement -> recommended events -> custom events -> custom dimensions
- **Data quality:** Separate test/production properties, set up internal traffic filters from day one, document all custom events, audit regularly with DebugView, export to BigQuery for backup