--- title: 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 filename="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](/docs/pages/building-your-application/routing/custom-document)