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How to add Google Analytics to your Next.js project

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Marouane Reda
Marouane Reda
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Add your Google Analytics ID to your Next.js .env.local file

After getting your Google Analytics ID from your Google Analytics account, add it to your .env.local file ( create the file in the root directory if it doesn't exist) :

NEXT_PUBLIC_GA_ID=<Your_tracking_ID>

Create functions to track pageviews and events

Create a file ( here named `gtag.js` under /lib) containing the custom functions to track pageviews and events on your site :
export const GA_TRACKING_ID = process.env.NEXT_PUBLIC_GA_ID

// https://developers.google.com/analytics/devguides/collection/gtagjs/pages
export const pageview = (url) => {
  window.gtag('config', GA_TRACKING_ID, {
    page_path: url,
  })
}

// https://developers.google.com/analytics/devguides/collection/gtagjs/events
export const event = ({ action, category, label, value }) => {
  window.gtag('event', action, {
    event_category: category,
    event_label: label,
    value: value,
  })
}

Add your Google Analytics ID to your app

In the _document.js file, we will add the tracking script wit our gtag ID (create _document.js in your root project if it doesn't exist):

import Document, { Html, Head, Main, NextScript } from 'next/document'

import { GA_TRACKING_ID } from '../lib/gtag'

export default class MyDocument extends Document {
  render() {
    return (
      <Html>
        <Head>
          {/* Global Site Tag (gtag.js) - Google Analytics */}
          <script
            async
            src={`https://www.googletagmanager.com/gtag/js?id=${GA_TRACKING_ID}`}
          />
          <script
            dangerouslySetInnerHTML={{
              __html: `
            window.dataLayer = window.dataLayer || [];
            function gtag(){dataLayer.push(arguments);}
            gtag('js', new Date());
            gtag('config', '${GA_TRACKING_ID}', {
              page_path: window.location.pathname,
            });
          `,
            }}
          />
        </Head>
        <body>
          <Main />
          <NextScript />
        </body>
      </Html>
    )
  }
}

Log pageviews in your Next.js app

Now modify your _app.js file by adding a useEffect hook where each change of route by the router will be tracked as a pageview

import { useEffect } from 'react'
import { useRouter } from 'next/router'
import * as gtag from '../lib/gtag'

const App = ({ Component, pageProps }) => {
  const router = useRouter()
  useEffect(() => {
    const handleRouteChange = (url) => {
      gtag.pageview(url)
    }
    router.events.on('routeChangeComplete', handleRouteChange)
    return () => {
      router.events.off('routeChangeComplete', handleRouteChange)
    }
  }, [router.events])

  return <Component {...pageProps} />
}

export default App

You are done! You should be able now to monitor your pages in Google Analytics.