react-code-dataset / next.js /docs /01-app /02-guides /analytics.mdx

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	---
	title: How to add analytics to your Next.js application
	nav_title: Analytics
	description: Measure and track page performance using Next.js Speed Insights
	---

	{/* The content of this doc is shared between the app and pages router. You can use the `<PagesOnly>Content</PagesOnly>` component to add content that is specific to the Pages Router. Any shared content should not be wrapped in a component. */}

	Next.js has built-in support for measuring and reporting performance metrics. You can either use the [`useReportWebVitals`](/docs/app/api-reference/functions/use-report-web-vitals) hook to manage reporting yourself, or alternatively, Vercel provides a [managed service](https://vercel.com/analytics?utm_source=next-site&utm_medium=docs&utm_campaign=next-website) to automatically collect and visualize metrics for you.

	## Client Instrumentation

	For more advanced analytics and monitoring needs, Next.js provides a `instrumentation-client.js\|ts` file that runs before your application's frontend code starts executing. This is ideal for setting up global analytics, error tracking, or performance monitoring tools.

	To use it, create an `instrumentation-client.js` or `instrumentation-client.ts` file in your application's root directory:

	```js filename="instrumentation-client.js"
	// Initialize analytics before the app starts
	console.log('Analytics initialized')

	// Set up global error tracking
	window.addEventListener('error', (event) => {
	// Send to your error tracking service
	reportError(event.error)
	})
	```

	## Build Your Own

	<PagesOnly>

	```jsx filename="pages/_app.js"
	import { useReportWebVitals } from 'next/web-vitals'

	function MyApp({ Component, pageProps }) {
	useReportWebVitals((metric) => {
	console.log(metric)
	})

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

	View the [API Reference](/docs/pages/api-reference/functions/use-report-web-vitals) for more information.

	</PagesOnly>

	<AppOnly>

	```jsx filename="app/_components/web-vitals.js"
	'use client'

	import { useReportWebVitals } from 'next/web-vitals'

	export function WebVitals() {
	useReportWebVitals((metric) => {
	console.log(metric)
	})
	}
	```

	```jsx filename="app/layout.js"
	import { WebVitals } from './_components/web-vitals'

	export default function Layout({ children }) {
	return (
	<html>
	<body>
	<WebVitals />
	{children}
	</body>
	</html>
	)
	}
	```

	> Since the `useReportWebVitals` hook requires the `'use client'` directive, the most performant approach is to create a separate component that the root layout imports. This confines the client boundary exclusively to the `WebVitals` component.

	View the [API Reference](/docs/app/api-reference/functions/use-report-web-vitals) for more information.

	</AppOnly>

	## Web Vitals

	[Web Vitals](https://web.dev/vitals/) are a set of useful metrics that aim to capture the user
	experience of a web page. The following web vitals are all included:

	- [Time to First Byte](https://developer.mozilla.org/docs/Glossary/Time_to_first_byte) (TTFB)
	- [First Contentful Paint](https://developer.mozilla.org/docs/Glossary/First_contentful_paint) (FCP)
	- [Largest Contentful Paint](https://web.dev/lcp/) (LCP)
	- [First Input Delay](https://web.dev/fid/) (FID)
	- [Cumulative Layout Shift](https://web.dev/cls/) (CLS)
	- [Interaction to Next Paint](https://web.dev/inp/) (INP)

	You can handle all the results of these metrics using the `name` property.

	<PagesOnly>

	```jsx filename="pages/_app.js"
	import { useReportWebVitals } from 'next/web-vitals'

	function MyApp({ Component, pageProps }) {
	useReportWebVitals((metric) => {
	switch (metric.name) {
	case 'FCP': {
	// handle FCP results
	}
	case 'LCP': {
	// handle LCP results
	}
	// ...
	}
	})

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

	</PagesOnly>

	<AppOnly>

	```tsx filename="app/_components/web-vitals.tsx" switcher
	'use client'

	import { useReportWebVitals } from 'next/web-vitals'

	export function WebVitals() {
	useReportWebVitals((metric) => {
	switch (metric.name) {
	case 'FCP': {
	// handle FCP results
	}
	case 'LCP': {
	// handle LCP results
	}
	// ...
	}
	})
	}
	```

	```jsx filename="app/_components/web-vitals.js" switcher
	'use client'

	import { useReportWebVitals } from 'next/web-vitals'

	export function WebVitals() {
	useReportWebVitals((metric) => {
	switch (metric.name) {
	case 'FCP': {
	// handle FCP results
	}
	case 'LCP': {
	// handle LCP results
	}
	// ...
	}
	})
	}
	```

	</AppOnly>

	<PagesOnly>

	## Custom Metrics

	In addition to the core metrics listed above, there are some additional custom metrics that
	measure the time it takes for the page to hydrate and render:

	- `Next.js-hydration`: Length of time it takes for the page to start and finish hydrating (in ms)
	- `Next.js-route-change-to-render`: Length of time it takes for a page to start rendering after a
	route change (in ms)
	- `Next.js-render`: Length of time it takes for a page to finish render after a route change (in ms)

	You can handle all the results of these metrics separately:

	```js
	export function reportWebVitals(metric) {
	switch (metric.name) {
	case 'Next.js-hydration':
	// handle hydration results
	break
	case 'Next.js-route-change-to-render':
	// handle route-change to render results
	break
	case 'Next.js-render':
	// handle render results
	break
	default:
	break
	}
	}
	```

	These metrics work in all browsers that support the [User Timing API](https://caniuse.com/#feat=user-timing).

	</PagesOnly>

	## Sending results to external systems

	You can send results to any endpoint to measure and track
	real user performance on your site. For example:

	```js
	useReportWebVitals((metric) => {
	const body = JSON.stringify(metric)
	const url = 'https://example.com/analytics'

	// Use `navigator.sendBeacon()` if available, falling back to `fetch()`.
	if (navigator.sendBeacon) {
	navigator.sendBeacon(url, body)
	} else {
	fetch(url, { body, method: 'POST', keepalive: true })
	}
	})
	```

	> Good to know: If you use [Google Analytics](https://analytics.google.com/analytics/web/), using the
	> `id` value can allow you to construct metric distributions manually (to calculate percentiles,
	> etc.)

	> ```js
	> useReportWebVitals((metric) => {
	> // Use `window.gtag` if you initialized Google Analytics as this example:
	> // https://github.com/vercel/next.js/blob/canary/examples/with-google-analytics
	> window.gtag('event', metric.name, {
	> value: Math.round(
	> metric.name === 'CLS' ? metric.value * 1000 : metric.value
	> ), // values must be integers
	> event_label: metric.id, // id unique to current page load
	> non_interaction: true, // avoids affecting bounce rate.
	> })
	> })
	> ```
	>
	> Read more about [sending results to Google Analytics](https://github.com/GoogleChrome/web-vitals#send-the-results-to-google-analytics).