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Compare out-of-the-box features between PDF.js and PDF.js Express. PDF.js is an open-source PDF library that was created by Mozilla in 2011 to let you open and render PDFs in web browsers using JavaScript. PDF.js Express is a fully-featured commercial PDF.js viewer with a modern and customizable UI.

Not sure if PDF.js is right for you? Read our PDF.js Buy vs Build Guide

When to use PDF.js:

  • Users need to view PDFs
  • UI/UX does not need to be a competitive differentiator
  • Users won’t need to zoom in to see details
  • The text search tool can miss some relevant text within a PDF

When to use PDF.js express:

  • Users need to view, annotate, form-fill, or sign PDFs
  • Your app needs a modern, highly customizable UI/UX
  • Users expect sharp graphics when zoomed in
  • The text search tool needs to find relevant text within a PDF
Open all
PDF.jsPDF.js Express
Max zoom factor (image depth / quality)



Crisp graphics at high zoomcheck
Collaborate in real-timecheck
Freehand, free text, shape, comment annotationscheck
Stamp document with text, imagescheck
Watermark to prevent distributioncheck
User roles and permissions (control access to each annotation)check
Annotation events to trigger custom functionalitycheck
Create custom annotationscheck
Cloudy annotationscheck
Measurement tools (distance, perimeter, area)check
addModern UI
Modern UI written in ReactJScheck
Fully responsivecheck
Dark themecheckcheck
Hide/Show Download/Print and other toolscheckcheck
Open source UI (source code downloadable)checkcheck
addPDF Forms
User form fillingcheck
Merging form datacheck
Programmatically prepopulate formscheck
Extract forms data and save values separatelycheck
JavaScript field validation/formattingcheck
Customize form appearancecheck
Print entered field valuescheck
Form actions/interaction between elementscheck
Sign by using hand-drawn annotationcheck
Save signatures for signing multiple pagescheck
Rendering engine

PDF.js open-source community

PDF.js open-source community

PDF Viewer UI

PDF.js open-source community

1-on-1 support via forum

Try it for free

With PDF.js Express you can easily add out-of-the-box
features to your PDF viewer

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