[WebViewer] Version Mismatch:

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
  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

    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}`);

Hello, I’m Ron, an automated tech support bot :robot:

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


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.