# \[WebViewer\] Version Mismatch:

**URL:** <https://pdfjs.community/t/webviewer-version-mismatch/1059>\
**Category:** Technical Support\
**Tags:** pdfjs-express\
**Created:** [October 10, 2021, 4:52pm UTC](https://pdfjs.community/t/webviewer-version-mismatch/1059 "2021-10-10T16:52:21Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![abe](https://yyz1.discourse-cdn.com/flex031/user_avatar/pdfjs.community/abe/32/565_2.png) [@abe](https://pdfjs.community/u/abe)\
**Post date:** [October 10, 2021, 4:52pm UTC](https://pdfjs.community/t/webviewer-version-mismatch/1059/1 "2021-10-10T16:52:21Z")

</div>

**PDF.js Express Version**

**Detailed description of issue**

1. I went through this tutorial and followed all steps: [PDF.js Express Viewer Download & Integration | Documentation](https://pdfjs.express/documentation/get-started-viewer/manually)
2. When I click F12 and use the developer’s tool, I see these errors:  
a. webviewer-ui.min.js:239  
[WebViewer] Version Mismatch: UI requires Core version 8.2.0 and above.  
b. webviewer-ui.min.js:68  
react-i18next:: It seems you are still using the old wait option, you may migrate to the new useSuspense behaviour.

**Expected behaviour**  
After following the tutorial, there should be no warning messages in the developer’s tools.

**Code snippet**

```javascript
<script>
  WebViewer({
    path: '/pdf9/lib', // path to the PDF.js Express'lib' folder on your server
    licenseKey: 'mXXXXX',
    initialDoc: 'https://pdftron.s3.amazonaws.com/downloads/pl/webviewer-demo.pdf',
    // initialDoc: '/path/to/my/file.pdf', // You can also use documents on your server
  }, document.getElementById('viewer'))
  .then(instance => {
    // now you can access APIs through the WebViewer instance
    const { Core, UI } = instance;

    // adding an event listener for when a document is loaded
    Core.documentViewer.addEventListener('documentLoaded', () => {
      console.log('document loaded');
    });

    // adding an event listener for when the page number has changed
    Core.documentViewer.addEventListener('pageNumberUpdated', (pageNumber) => {
      console.log(`Page number is: ${pageNumber}`);
    });
  });
</script>

```

---

<div class="post-metadata">

**Author:** ![system](https://canada1.discourse-cdn.com/flex031/uploads/pdfjscommunity/original/1X/ffbcd25c7d423db8d5acd5db201c272f4db306dd.png) [@system](https://pdfjs.community/u/system)\
**Post date:** [October 10, 2021, 4:52pm UTC](https://pdfjs.community/t/webviewer-version-mismatch/1059/2 "2021-10-10T16:52:25Z")

</div>

**Hello, I’m Ron, an automated tech support bot 🤖**

While you wait for one of our customer support representatives to get back to you, please check out some of these documentation pages:

Guides:
- [What is PDF.js Express? - Details of instantiation](https://pdfjs.express/documentation/learn-more/inside-express-viewer.8#details-of-instantiation)
- [Angular project WebViewer integration issues](https://pdfjs.express/documentation/get-started-viewer/angular/angular-integration-issues)
- [Remove annotations in viewer](https://pdfjs.express/documentation/annotation/remove-annotations)

APIs:
- [UI - dangerouslySetNoteTransformFunction(noteTransformFunction)](https://pdfjs.express/api/UI.html#.dangerouslySetNoteTransformFunction__anchor)
- [UndefinedWebViewer(options, viewerElement)](https://pdfjs.express/api/global.html#WebViewer__anchor)
- [Core - getVersion()](https://pdfjs.express/api/Core.html#.getVersion__anchor)

Forums:
- [Cannot read property ‘name’ of undefined (core 7.3.2, CoreControls.js:697)](https://pdfjs.community/t/cannot-read-property-name-of-undefined-core-7-3-2-corecontrols-js-697/770/1)
- [WebViewer not being initialized in firefox](https://pdfjs.community/t/webviewer-not-being-initialized-in-firefox/435/1)
- [How do I set up the core for Advanced customization?](https://pdfjs.community/t/how-do-i-set-up-the-core-for-advanced-customization/226/1)

---

<div class="post-metadata">

**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:** [October 12, 2021, 2:18pm UTC](https://pdfjs.community/t/webviewer-version-mismatch/1059/3 "2021-10-12T14:18:47Z")

</div>

Hey there!

This is intended for now. We will remove this warning message in a future release, but for now you can safely ignore it.

Logan