--- 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 `Content` 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 ```jsx filename="pages/_app.js" import { useReportWebVitals } from 'next/web-vitals' function MyApp({ Component, pageProps }) { useReportWebVitals((metric) => { console.log(metric) }) return } ``` View the [API Reference](/docs/pages/api-reference/functions/use-report-web-vitals) for more information. ```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 ( {children} ) } ``` > 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. ## 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. ```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 } ``` ```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 } // ... } }) } ``` ## 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). ## 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).