### Experimental
Introduce `next/vitals` and `useExperimentalWebVitalsReport` API which is not limited by `_app`.
`pages/index.js`
```jsx
import { useExperimentalWebVitalsReport } from 'next/vitals'
export default function Index() {
useExperimentalWebVitalsReport((metric) => {
// handle metric...
})
return 'sup'
}
```