# How do I set up the core for Advanced customization? **URL:** \ **Category:** Technical Support\ **Tags:** pdfjs-express\ **Created:** [August 24, 2020, 9:03am UTC](https://pdfjs.community/t/how-do-i-set-up-the-core-for-advanced-customization/226 "2020-08-24T09:03:18Z")\ **Posts on this page:** 1\ **Showing post:** 2
**Author:** ![Logan](https://yyz1.discourse-cdn.com/flex031/user_avatar/pdfjs.community/logan/32/13_2.png) [@Logan](https://pdfjs.community/u/Logan)\ **Post date:** [August 24, 2020, 3:01pm UTC](https://pdfjs.community/t/how-do-i-set-up-the-core-for-advanced-customization/226/2 "2020-08-24T15:01:03Z")
Hi there, There is some additional configuration that needs to be done to make the UI work with the PDF.js Express Core. We are going to spend some time figuring out how to make this easier for everyone, and then get back to you with an easier solution! For now, you have to replace the `index.html` file in the UI to this: ```javascript WebViewer UI
``` If this doesn’t work please let me know. Thank you! Logan --- _[View the full topic](https://pdfjs.community/t/how-do-i-set-up-the-core-for-advanced-customization/226)._