# Blazor Demo Error

**URL:** <https://pdfjs.community/t/blazor-demo-error/342>\
**Category:** Technical Support\
**Created:** [October 16, 2020, 9:41am UTC](https://pdfjs.community/t/blazor-demo-error/342 "2020-10-16T09:41:45Z")\
**Posts on this page:** 1\
**Showing post:** 1

<div class="post-metadata">

**Author:** ![bedmondson](https://avatars.discourse-cdn.com/v4/letter/b/a88e57/32.png) [@bedmondson](https://pdfjs.community/u/bedmondson)\
**Post date:** [October 16, 2020, 9:41am UTC](https://pdfjs.community/t/blazor-demo-error/342/1 "2020-10-16T09:41:45Z")

</div>

The Blazor Demo has a missing component.

When you follow the steps for the blazor demo ([https://pdfjs.express/documentation/get-started/blazor/new-project](https://pdfjs.express/documentation/get-started/blazor/new-project)). When you view the webviewer page you are presented an exception that “Microsoft.JSInterop.JSException: WebViewer is not defined”.

To fix I had to manually add “webviewer.min.js” to the lib directory.

It works for me now but thought others might have the same issue.

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_[View the full topic](https://pdfjs.community/t/blazor-demo-error/342)._