# Loading & Zoom of PDF takes several minutes

**URL:** <https://pdfjs.community/t/loading-zoom-of-pdf-takes-several-minutes/1232>\
**Category:** Technical Support\
**Created:** [December 8, 2021, 2:32pm UTC](https://pdfjs.community/t/loading-zoom-of-pdf-takes-several-minutes/1232 "2021-12-08T14:32:40Z")\
**Posts on this page:** 1\
**Showing post:** 6

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**Author:** ![user39](https://avatars.discourse-cdn.com/v4/letter/u/59ef9b/32.png) [@user39](https://pdfjs.community/u/user39)\
**Post date:** [December 9, 2021, 5:02pm UTC](https://pdfjs.community/t/loading-zoom-of-pdf-takes-several-minutes/1232/6 "2021-12-09T17:02:32Z")

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Hi Logan,

so it means that PDF.js Express is based on PDF.js and not on the Engine which PDFTron is using?  
But using the original PDF.js viewer from Firefox itself loads this file faster as well as the current PDF.js Express version.

Link to the other bug: [Wrong encoding inside PDF](https://pdfjs.community/t/wrong-encoding-inside-pdf/1236)

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