Question

Why does "window is not defined" error occur in Next.js?

I'm encountering the "window is not defined" error in Next.js and am unsure why it’s happening. I understand that Next.js uses server-side rendering, but I'm not sure how to handle client-side objects like window in this environment. Could someone explain why this error occurs and how to properly handle such cases in Next.js?

Answer 1

"window is not defined" error in Next.js The root cause of this is that Next.js is a framework to create server-rendered or statically generated React applications. In server-side rendering, it executes on the server where window does not exist because it is a browser-specific global object.

Why This Happens

The object window is implemented in the browser environment, hence unavailable during server-side rendering. This error occurs when browser-specific globals, such as window or localStorage, are accessed trying to access in Next.js apps without proper handling of SSR.