reactStrictMode

Good to know: Since Next.js 13.5.1, Strict Mode is true by default with app router, so the above configuration is only necessary for pages. You can still disable Strict Mode by setting reactStrictMode: false.

Suggested: We strongly suggest you enable Strict Mode in your Next.js application to better prepare your application for the future of React.

React's Strict Mode is a development mode only feature for highlighting potential problems in an application. It helps to identify unsafe lifecycles, legacy API usage, and a number of other features.

The Next.js runtime is Strict Mode-compliant. To opt-in to Strict Mode, configure the following option in your next.config.js:

module.exports = {
  reactStrictMode: true,
}

If you or your team are not ready to use Strict Mode in your entire application, that's OK! You can incrementally migrate on a page-by-page basis using <React.StrictMode>.