# A valid license key is required to use the view only build of PDF.js Express

**URL:** <https://pdfjs.community/t/a-valid-license-key-is-required-to-use-the-view-only-build-of-pdf-js-express/1607>\
**Category:** Technical Support\
**Tags:** pdfjs-express\
**Created:** [April 19, 2022, 3:39pm UTC](https://pdfjs.community/t/a-valid-license-key-is-required-to-use-the-view-only-build-of-pdf-js-express/1607 "2022-04-19T15:39:37Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![devel0per95](https://yyz1.discourse-cdn.com/flex031/user_avatar/pdfjs.community/devel0per95/32/738_2.png) [@devel0per95](https://pdfjs.community/u/devel0per95)\
**Post date:** [April 19, 2022, 3:39pm UTC](https://pdfjs.community/t/a-valid-license-key-is-required-to-use-the-view-only-build-of-pdf-js-express/1607/1 "2022-04-19T15:39:38Z")

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Hello, i want help with this,  
when i launch this in local host using VSCODE  
in the console is asking for the license key,  
i have created a license key for the viewer version, but the error isn’t going!

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<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:** [April 19, 2022, 3:39pm UTC](https://pdfjs.community/t/a-valid-license-key-is-required-to-use-the-view-only-build-of-pdf-js-express/1607/3 "2022-04-19T15:39:43Z")

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**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:
- [Integrating PDF.js Express Plus into a new Blazor project - Prerequisites](https://pdfjs.express/documentation/get-started/blazor/new-project#prerequisites)
- [Adding your license key - PDF.js Express Viewer License Keys](https://pdfjs.express/documentation/get-started/add-license-key#pdf.js-express-viewer-license-keys-<span-class='viewer'></span>)
- [Manually download and integrate PDF.js Express Viewer](https://pdfjs.express/documentation/get-started-viewer/manually)

APIs:
- [Core - preloadPDFWorker(pdfBackendType, workerHandlers)](https://pdfjs.express/api/Core.html#.preloadPDFWorker__anchor)
- [PDF.js Express Utilities](https://pdfjs.express/api/utils/index.html#__anchor)
- [ExpressUtils(optionsopt) - # async extract() → {Promise.}](https://pdfjs.express/api/utils/ExpressUtils.html#extract__anchor)

Forums:
- [I have license, but still show watermark](https://pdfjs.community/t/i-have-license-but-still-show-watermark/1078/6)
- [License key for viewer is not working in an ionic app](https://pdfjs.community/t/license-key-for-viewer-is-not-working-in-an-ionic-app/1436/1)
- [Licence key not working with version 8.2](https://pdfjs.community/t/licence-key-not-working-with-version-8-2/1310/1)

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<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:** [April 20, 2022, 2:14pm UTC](https://pdfjs.community/t/a-valid-license-key-is-required-to-use-the-view-only-build-of-pdf-js-express/1607/4 "2022-04-20T14:14:50Z")

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Hi,

Please try the debugging steps [posted here](https://pdfjs.community/t/pdf-js-express-viewer-watermarks/1614/4) and see if that helps.

If none of those things help, let me know!

Thanks,  
Logan