Warning: Text content did not match. Server: “I’m out” Client: “I’m in” div

Next.js pre-renders every page on the server. This means that Next.js generates HTML for each page in advance, instead of having it all done by client-side JavaScript. (…) When a page is loaded by the browser, its JavaScript code runs and makes the page fully interactive. (This process is called hydration.) The HTML rendered on … Read more

useRouter/withRouter receive undefined on query in first render

I found something: isReady: boolean – Whether the router fields are updated client-side and ready for use. Should only be used inside of useEffect methods and not for conditionally rendering on the server. https://nextjs.org/docs/api-reference/next/router#router-object And the code would be like: const router = useRouter(); useEffect(()=>{ if(!router.isReady) return; // codes using router.query }, [router.isReady]);

Why are cookies not sent to the server via getServerSideProps in Next.js?

That’s because the request inside getServerSideProps doesn’t run in the browser – where cookies are automatically sent on every request – but actually gets executed on the server, in a Node.js environment. This means you need to explicitly pass the cookies to the axios request to send them through. export async function getServerSideProps({ req }) … Read more

Internal API fetch with getServerSideProps? (Next.js)

But then I read in the Next.js documentation that you should not use fetch() to all an API route in getServerSideProps(). You want to use the logic that’s in your API route directly in getServerSideProps, rather than calling your internal API. That’s because getServerSideProps runs on the server just like the API routes (making a … Read more

How to add new pages without rebuilding an app with +150k static pages?

That can be achieved with getStaticProps/getStaticPaths. You’ll have to use fallback: true or fallback: ‘blocking’ in getStaticPaths. With fallback: true the paths not generated at build time will serve a fallback page on the first request while Next.js statically generates the page. When this is done the page will be swapped from the fallback page … Read more

Window is not defined in Next.js React app

̶A̶n̶o̶t̶h̶e̶r̶ ̶s̶o̶l̶u̶t̶i̶o̶n̶ ̶i̶s̶ ̶b̶y̶ ̶u̶s̶i̶n̶g̶ ̶p̶r̶o̶c̶e̶s̶s̶.̶b̶r̶o̶w̶s̶e̶r ̶ ̶t̶o̶ ̶j̶u̶s̶t̶ ̶e̶x̶e̶c̶u̶t̶e̶ ̶ ̶y̶o̶u̶r̶ ̶c̶o̶m̶m̶a̶n̶d̶ ̶d̶u̶r̶i̶n̶g̶ ̶r̶e̶n̶d̶e̶r̶i̶n̶g̶ ̶o̶n̶ ̶t̶h̶e̶ ̶c̶l̶i̶e̶n̶t̶ ̶s̶i̶d̶e̶ ̶o̶n̶l̶y̶. But process object has been deprecated in Webpack5 and also NextJS, because it is a NodeJS variable for backend side only. So we have to use back window object from the browser. if (typeof window … Read more

Fetch error when building Next.js static website in production

You should not call an internal API route inside getStaticProps. Instead, you can safely use your API logic directly in getStaticProps/getStaticPaths. These only happen server-side so you can write server-side code directly. As getStaticProps runs only on the server-side, it will never run on the client-side. It won’t even be included in the JS bundle … Read more