# Licence validation error

**URL:** <https://pdfjs.community/t/licence-validation-error/3706>\
**Category:** Technical Support\
**Tags:** pdfjs-express\
**Created:** [May 22, 2025, 8:44am UTC](https://pdfjs.community/t/licence-validation-error/3706 "2025-05-22T08:44:25Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![arielrobert.custrin](https://avatars.discourse-cdn.com/v4/letter/a/9d8465/32.png) [@arielrobert.custrin](https://pdfjs.community/u/arielrobert.custrin)\
**Post date:** [May 22, 2025, 8:44am UTC](https://pdfjs.community/t/licence-validation-error/3706/1 "2025-05-22T08:44:25Z")

</div>

**Which product are you using?**  
PDF.js Express Viewer

**PDF.js Express Version**  
8.7.5

**Detailed description of issue**  
My app is in dotNet 9 (Blazor) and I’m using the stadalone library installed manually with PDFJSExpress-view-only.zip  
Can’t validate licence key, because in ([https://auth.pdfjs.express/?key=](https://auth.pdfjs.express/?key=)) request header Origin is not set.  
Same also when running in local environment is not picking as localhost.

---

<div class="post-metadata">

**Author:** ![kkim](https://avatars.discourse-cdn.com/v4/letter/k/3ab097/32.png) [@kkim](https://pdfjs.community/u/kkim)\
**Post date:** [May 22, 2025, 4:32pm UTC](https://pdfjs.community/t/licence-validation-error/3706/3 "2025-05-22T16:32:46Z")

</div>

Hi there,

Thank you for contacting PDFJS Forums.

To add your license key, please make sure it is referenced in the constructor. More information can be found here: [PDF.js Express Viewer Download & Integration | Documentation](https://pdfjs.express/documentation/get-started/add-license-key)

Our Blazor guide can also be found here which explains how to integrate the standalone PDFJS library: [Integrate JavaScript PDF Library & Blazor | PDF.js Express SDK](https://pdfjs.express/documentation/get-started/blazor/new-project)

best regards,  
Kevin

---

<div class="post-metadata">

**Author:** ![arielrobert.custrin](https://avatars.discourse-cdn.com/v4/letter/a/9d8465/32.png) [@arielrobert.custrin](https://pdfjs.community/u/arielrobert.custrin)\
**Post date:** [May 23, 2025, 8:37am UTC](https://pdfjs.community/t/licence-validation-error/3706/4 "2025-05-23T08:37:42Z")

</div>

Thanks for the reply.  
It was my fault I guess. I was using my browser with disabled security (no-cors) and so the Origin header was not setting…