NextJS ‘window is not defined’

Lets say you are using NextJS and want to check the window location path:

If you are currently in development mode, you will probably run into this error:

The problem is that during getInitialProps NextJS will render your component once. The node process doesn’t have a window object.

You heard that NextJS 10 populates the process.browser object that will work easily:

The problem is that according to these sources process.browser is deprecated. We should use typeof window === 'undefined' instead.

Here is a simple util function that you can copy:
export const isServer = () => typeof window === 'undefined'

If you don’t render your component on the server side, your build works again:

Voila! Component is rendering again.