reactStrictMode
Good to know: Since Next.js 13.4, 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:
next.config.js module.exports = {
  reactStrictMode: true,
}