@emotion/babel-plugin depends on some modules which require fs which obviously cannot be imported in the browser. (Furthermore, it's unclear if Next.js will allow you to require fs during SSR, if the require is located in code that is shared between client and server.)

So to get @emotion/babel-plugin to work in the browser / Next.js, we have to stub out any dependencies which require fs. This works via Webpack require.alias in next.config.js.

This is a very hacky workaround that could easily break things in the future.