🦞
add-analytics

Add Google Analytics 4 tracking to any project.
SKILL.md
---
name: add-analytics
description: Add Google Analytics 4 tracking to any project. Detects framework, adds tracking code, sets up events, and configures privacy settings.
argument-hint: "<measurement-id> [--events] [--consent] [--debug]"
---

# Google Analytics 4 Setup Skill

You are setting up Google Analytics 4 (GA4) for a project. Follow this comprehensive guide to add analytics properly.

## Arguments

Parse the following from `$ARGUMENTS`:
- **Measurement ID**: Format `G-XXXXXXXXXX` (required, ask if not provided)
- **--events**: Include custom event tracking helpers
- **--consent**: Include cookie consent integration
- **--debug**: Enable debug mode for development

## Step 1: Detect Project Type

Scan the project to determine the framework/setup:

```
Priority detection order:
1. next.config.js/ts → Next.js
2. nuxt.config.js/ts → Nuxt.js
3. astro.config.mjs → Astro
4. svelte.config.js → SvelteKit
5. remix.config.js → Remix
6. gatsby-config.js → Gatsby
7. vite.config.js + src/App.vue → Vue + Vite
8. vite.config.js + src/App.tsx → React + Vite
9. angular.json → Angular
10. package.json with "react-scripts" → Create React App
11. index.html only → Plain HTML
12. _app.tsx/jsx → Next.js (App Router check: app/ directory)
```

Also check for:
- TypeScript usage (tsconfig.json)
- Existing analytics (search for gtag, GA, analytics)
- Package manager (pnpm-lock.yaml, yarn.lock, package-lock.json)

## Step 2: Validate Measurement ID

The Measurement ID must:
- Start with `G-` (GA4 format)
- Be followed by exactly 10 alphanumeric characters
- Example: `G-ABC1234567`

If the user provides a `UA-` ID, inform them:
> "You provided a Universal Analytics ID (UA-). GA4 uses Measurement IDs starting with 'G-'.
> Universal Analytics was sunset in July 2024. You'll need to create a GA4 property at analytics.google.com"

## Step 3: Implementation by Framework

### Next.js (App Router - app/ directory)

Create `app/layout.tsx` modification or create `components/GoogleAnalytics.tsx`:

```tsx
// components/GoogleAnalytics.tsx
'use client'

import Script from 'next/script'

interface GoogleAnalyticsProps {
  measurementId: string
}

export function GoogleAnalytics({ measurementId }: GoogleAnalyticsProps) {
  return (
    <>
      <Script
        src={`https://www.googletagmanager.com/gtag/js?id=${measurementId}`}
        strategy="afterInteractive"
      />
      <Script id="google-analytics" strategy="afterInteractive">
        {`
          window.dataLayer = window.dataLayer || [];
          function gtag(){dataLayer.push(arguments);}
          gtag('js', new Date());
          gtag('config', '${measurementId}');
        `}
      </Script>
    </>
  )
}
```

Add to root layout:
```tsx
// app/layout.tsx
import { GoogleAnalytics } from '@/components/GoogleAnalytics'

// Add inside <body> or <html>:
<GoogleAnalytics measurementId="G-XXXXXXXXXX" />
```

### Next.js (Pages Router - pages/ directory)

Modify `pages/_app.tsx`:

```tsx
// pages/_app.tsx
import type { AppProps } from 'next/app'
import Script from 'next/script'

const GA_MEASUREMENT_ID = process.env.NEXT_PUBLIC_GA_MEASUREMENT_ID

export default function App({ Component, pageProps }: AppProps) {
  return (
    <>
      <Script
        src={`https://www.googletagmanager.com/gtag/js?id=${GA_MEASUREMENT_ID}`}
        strategy="afterInteractive"
      />
      <Script id="google-analytics" strategy="afterInteractive">
        {`
          window.dataLayer = window.dataLayer || [];
          function gtag(){dataLayer.push(arguments);}
          gtag('js', new Date());
          gtag('config', '${GA_MEASUREMENT_ID}');
        `}
      </Script>
      <Component {...pageProps} />
    </>
  )
}
```

### React (Vite/CRA)

Create `src/lib/analytics.ts`:

```typescript
// src/lib/analytics.ts
export const GA_MEASUREMENT_ID = import.meta.env.VITE_GA_MEASUREMENT_ID

declare global {
  interface Window {
    gtag: (...args: unknown[]) => void
    dataLayer: unknown[]
  }
}

export const initGA = () => {
  if (typeof window === 'undefined') return

  const script = document.createElement('script')
  script.src = `https://www.googletagmanager.com/gtag/js?id=${GA_MEASUREMENT_ID}`
  script.async = true
  document.head.appendChild(script)

  window.dataLayer = window.dataLayer || []
  window.gtag = function gtag() {
    window.dataLayer.push(arguments)
  }
  window.gtag('js', new Date())
  window.gtag('config', GA_MEASUREMENT_ID)
}

export const pageview = (url: string) => {
  window.gtag('config', GA_MEASUREMENT_ID, {
    page_path: url,
  })
}

export const event = (action: string, params?: Record<string, unknown>) => {
  window.gtag('event', action, params)
}
```

Initialize in `src/main.tsx`:

```tsx
import { initGA } from './lib/analytics'

// Initialize before render
if (import.meta.env.PROD) {
  initGA()
}
```

### Vue 3 (Vite)

Create `src/plugins/analytics.ts`:

```typescript
// src/plugins/analytics.ts
import type { App } from 'vue'
import type { Router } from 'vue-router'

const GA_MEASUREMENT_ID = import.meta.env.VITE_GA_MEASUREMENT_ID

declare global {
  interface Window {
    gtag: (...args: unknown[]) => void
    dataLayer: unknown[]
  }
}

export const analyticsPlugin = {
  install(app: App, { router }: { router: Router }) {
    // Load gtag script
    const script = document.createElement('script')
    script.src = `https://www.googletagmanager.com/gtag/js?id=${GA_MEASUREMENT_ID}`
    script.async = true
    document.head.appendChild(script)

    window.dataLayer = window.dataLayer || []
    window.gtag = function gtag() {
      window.dataLayer.push(arguments)
    }
    window.gtag('js', new Date())
    window.gtag('config', GA_MEASUREMENT_ID)

    // Track route changes
    router.afterEach((to) => {
      window.gtag('config', GA_MEASUREMENT_ID, {
        page_path: to.fullPath,
      })
    })

    // Provide global methods
    app.config.globalProperties.$gtag = window.gtag
  }
}
```

### Nuxt 3

Create `plugins/analytics.client.ts`:

```typescript
// plugins/analytics.client.ts
export default defineNuxtPlugin(() => {
  const config = useRuntimeConfig()
  const measurementId = config.public.gaMeasurementId

  if (!measurementId) return

  // Load gtag
  useHead({
    script: [
      {
        src: `https://www.googletagmanager.com/gtag/js?id=${measurementId}`,
        async: true,
      },
      {
        innerHTML: `
          window.dataLayer = window.dataLayer || [];
          function gtag(){dataLayer.push(arguments);}
          gtag('js', new Date());
          gtag('config', '${measurementId}');
        `,
      },
    ],
  })

  // Track route changes
  const router = useRouter()
  router.afterEach((to) => {
    window.gtag('config', measurementId, {
      page_path: to.fullPath,
    })
  })
})
```

Add to `nuxt.config.ts`:

```typescript
export default defineNuxtConfig({
  runtimeConfig: {
    public: {
      gaMeasurementId: process.env.NUXT_PUBLIC_GA_MEASUREMENT_ID,
    },
  },
})
```

### Astro

Create `src/components/Analytics.astro`:

```astro
---
// src/components/Analytics.astro
interface Props {
  measurementId: string
}

const { measurementId } = Astro.props
---

<script
  is:inline
  define:vars={{ measurementId }}
  src={`https://www.googletagmanager.com/gtag/js?id=${measurementId}`}
></script>

<script is:inline define:vars={{ measurementId }}>
  window.dataLayer = window.dataLayer || [];
  function gtag() {
    dataLayer.push(arguments);
  }
  gtag('js', new Date());
  gtag('config', measurementId);
</script>
```

Add to layout:

```astro
---
import Analytics from '../components/Analytics.astro'
---
<html>
  <head>
    <Analytics measurementId="G-XXXXXXXXXX" />
  </head>
</html>
```

### SvelteKit

Create `src/lib/analytics.ts` and `src/routes/+layout.svelte`:

```typescript
// src/lib/analytics.ts
import { browser } from '$app/environment'

export const GA_MEASUREMENT_ID = import.meta.env.VITE_GA_MEASUREMENT_ID

export function initGA() {
  if (!browser) return

  const script = document.createElement('script')
  script.src = `https://www.googletagmanager.com/gtag/js?id=${GA_MEASUREMENT_ID}`
  script.async = true
  document.head.appendChild(script)

  window.dataLayer = window.dataLayer || []
  window.gtag = function gtag() {
    window.dataLayer.push(arguments)
  }
  window.gtag('js', new Date())
  window.gtag('config', GA_MEASUREMENT_ID)
}

export function trackPageview(url: string) {
  if (!browser) return
  window.gtag('config', GA_MEASUREMENT_ID, { page_path: url })
}
```

```svelte
<!-- src/routes/+layout.svelte -->
<script lang="ts">
  import { onMount } from 'svelte'
  import { page } from '$app/stores'
  import { initGA, trackPageview } from '$lib/analytics'

  onMount(() => {
    initGA()
  })

  $: if ($page.url.pathname) {
    trackPageview($page.url.pathname)
  }
</script>

<slot />
```

### Plain HTML

Add to `<head>`:

```html
<!-- Google Analytics -->
<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>
```

## Step 4: Environment Variables

Create or update `.env` / `.env.local`:

```bash
# For Next.js
NEXT_PUBLIC_GA_MEASUREMENT_ID=G-XXXXXXXXXX

# For Vite (React/Vue/Svelte)
VITE_GA_MEASUREMENT_ID=G-XXXXXXXXXX

# For Nuxt
NUXT_PUBLIC_GA_MEASUREMENT_ID=G-XXXXXXXXXX
```

Add to `.env.example` if it exists (without the actual ID):

```bash
# Google Analytics 4 Measurement ID
NEXT_PUBLIC_GA_MEASUREMENT_ID=G-XXXXXXXXXX
```

**IMPORTANT**: Add `.env.local` to `.gitignore` if not already present.

## Step 5: Event Tracking Helpers (if --events flag)

Create a comprehensive events utility:

```typescript
// lib/analytics-events.ts

/**
 * GA4 Event Tracking Utilities
 *
 * Recommended events: https://support.google.com/analytics/answer/9267735
 */

type GTagEvent = {
  action: string
  category?: string
  label?: string
  value?: num

... (truncated)