nikcap / nextjs-google-analytics

Google Analytics for Next.js

Nextjs Google Analytics

Google Analytics for Next.js

This package optimizes script loading using Next.js Script tag, which means that it will only work on apps using Next.js >= 11.0.0.

Installation

npm install --save nextjs-google-analytics

Usage

Your Google Analytics measurement id is read from NEXT_PUBLIC_GA_MEASUREMENT_ID environment variable, so make sure it is set in your production environment:

• Vercel
• Netlify

If the variable is not set or is empty, nothing will be loaded, making it safe to work in development.

To load it and test it on development, add:

NEXT_PUBLIC_GA_MEASUREMENT_ID="G-XXXXXXXXXX"

to your .env.local file.

As an alternative, you can use the gaMeasurementId param to pass your Google Analytics measurement id.

The NEXT_PUBLIC_GA_MEASUREMENT_ID environment variable will take precedence over the gaMeasurementId param, so if both are set with different values, the environment variable will override the param.

Scripts

Use the GoogleAnalytics component to load the gtag scripts. You can add it to a custom App component and this will take care of including the necessary scripts for every page (or you could add it on a per page basis if you need more control):

// pages/_app.js
import { GoogleAnalytics } from "nextjs-google-analytics";

const App = ({ Component, pageProps }) => {
  return (
    <>
      <GoogleAnalytics />
      <Component {...pageProps} />
    </>
  );
};

export default App;

By default, scripts are loaded using the afterInteractive strategy, which means they are injected on the client-side and will run after hydration.

If you need more control, the component exposes the strategy prop to control how the scripts are loaded:

// pages/_app.js
import { GoogleAnalytics } from "nextjs-google-analytics";

const App = ({ Component, pageProps }) => {
  return (
    <>
      <GoogleAnalytics strategy="lazyOnload" />
      <Component {...pageProps} />
    </>
  );
};

export default App;

Page views

To track all pages views, call the usePageViews hook inside a custom App component, make sure to include the necessary gtag scripts with the GoogleAnalytics component:

// pages/_app.js
import { GoogleAnalytics, usePageViews } from "nextjs-google-analytics";

const App = ({ Component, pageProps }) => {
  usePageViews();

  return (
    <>
      <GoogleAnalytics />
      <Component {...pageProps} />
    </>
  );
};

export default App;

The module also exports a pageView function that you can use if you need more control.

Custom event

You can use the event function to track a custom event:

import { useState } from "react";
import Page from "../components/Page";
import { event } from "nextjs-google-analytics";

export function Contact() {
  const [message, setMessage] = useState("");

  const handleInput = (e) => {
    setMessage(e.target.value);
  };

  const handleSubmit = (e) => {
    e.preventDefault();

    event("submit_form", {
      category: "Contact",
      label: message,
    });

    setState("");
  };

  return (
    <Page>
      <h1>This is the Contact page</h1>
      <form onSubmit={handleSubmit}>
        <label>
          <span>Message:</span>
          <textarea onChange={handleInput} value={message} />
        </label>
        <button type="submit">submit</button>
      </form>
    </Page>
  );
}

Web Vitals

To send Next.js web vitals to Google Analytics you can use a custom event on the reportWebVitals function inside a custom App component:

// pages/_app.js
import { GoogleAnalytics, event } from "nextjs-google-analytics";

export function reportWebVitals({ id, name, label, value }) {
  event(name, {
    category: label === "web-vital" ? "Web Vitals" : "Next.js custom metric",
    value: Math.round(name === "CLS" ? value * 1000 : value), // values must be integers
    label: id, // id unique to current page load
    nonInteraction: true, // avoids affecting bounce rate.
  });
}

const App = ({ Component, pageProps }) => {
  return (
    <>
      <GoogleAnalytics />
      <Component {...pageProps} />
    </>
  );
};

export default App;

If you are using TypeScript, you can import NextWebVitalsMetric from next/app:

import type { NextWebVitalsMetric } from "next/app";

export function reportWebVitals(metric: NextWebVitalsMetric) {
  // ...
}

Using the gaMeasurementId param

All exported components, hooks, and functions, accept an optional gaMeasurementId param that can be used in case no environment variable is provided:

// pages/_app.js
import { GoogleAnalytics, event } from "nextjs-google-analytics";
import { gaMeasurementId } from "./lib/gtag";

export function reportWebVitals({
  id,
  name,
  label,
  value,
}: NextWebVitalsMetric) {
  event(
    name,
    {
      category: label === "web-vital" ? "Web Vitals" : "Next.js custom metric",
      value: Math.round(name === "CLS" ? value * 1000 : value), // values must be integers
      label: id, // id unique to current page load
      nonInteraction: true, // avoids affecting bounce rate.
    },
    gaMeasurementId
  );
}
const App = ({ Component, pageProps }) => {
  usePageViews({ gaMeasurementId });

  return (
    <>
      <GoogleAnalytics gaMeasurementId={gaMeasurementId} />
      <Component {...pageProps} />
    </>
  );
};

export default App;

Debugging you Google Analytics

1. Install the Google Analytics Debugger.

2. Turn it on by clicking its icon to the right of the address bar.

3. Open the Chrome Javascript console to see the messages.

   On Windows and Linux, press Control-Shift-J.

   On Mac, press Command-Option-J.

4. Refresh the page you are on.

TypeScript

The module is written in TypeScript and type definitions are included.

Contributing

Contributions, issues and feature requests are welcome!

Show your support

Give a ⭐️ if you like this project!

LICENSE

MIT