# Fix the 'module not found' error in Next.js

> Fix the Next.js Module not found: Can't resolve 'net' error, caused by running backend code on the client; move that library call into getStaticProps instead.

Author: [Flavio Copes](https://flaviocopes.com/about/) | Published: 2021-06-30 | Topics: [Next.js](https://flaviocopes.com/tags/next/) | Canonical: https://flaviocopes.com/nextjs-fix-module-not-found/

While doing some sanitization on a variable in [Next.js](https://flaviocopes.com/nextjs/) I ran into this weird problem:

```
Module not found: Error: Can't resolve 'net'
```

You might have some variation of it, which says a core [Node.js](https://flaviocopes.com/nodejs/) module is missing.

Do NOT `npm install net` or anything like that. If you already tried, run `npm uninstall` on those modules.

The problem is this: Next.js is trying to run backend code in the frontend.

In my case it was the [DOMPurify](https://github.com/cure53/DOMPurify) library. I was using it inside the component, but instead I had to use it in the `getStaticProps()` method.

That method runs at build time in the Node environment, where that library expected to be ran into.