# No Duplicate Head > Prevent duplicate usage of `` in `pages/_document.js`. ### Why This Error Occurred More than a single instance of the `` component was used in a single custom document. This can cause unexpected behavior in your application. ### Possible Ways to Fix It Only use a single `` component in your custom document in `pages/_document.js`. ```jsx // pages/_document.js import Document, { Html, Head, Main, NextScript } from 'next/document' class MyDocument extends Document { static async getInitialProps(ctx) { //... } render() { return (

) } } export default MyDocument ``` ### Useful Links - [Custom Document](https://nextjs.org/docs/advanced-features/custom-document)