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ViewerJS is a project initially created by KO GmbH. It is open-source and commercial at the same time.


We are using GitHub for communicating about features/issues with the community.


ViewerJS is commercially supported. It can be used in your software and we can add features and help you with that!

What is ViewerJS?

ViewerJS is a combination of a number of excellent open source tools that are built on HTML and JavaScript. ViewerJS was funded by NLnet foundation, consider a donation.

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The heavy lifting in ViewerJS is done by these awesome projects:

PDF.js (by Mozilla)

PDF.js logo

PDF.js is a library created by Andreas Gal and others at Mozilla Labs. It is an HTML5 technology experiment that explores building a faithful and efficient Portable Document Format (PDF) renderer without native code assistance. PDF.js is community-driven and supported by Mozilla Labs. Its goal is to create a general-purpose, web standards-based platform for parsing and rendering PDFs, and eventually release a PDF reader extension powered by PDF.js.
Visit project website

WebODF (by KO GmbH)

WebODF logo

WebODF is a JavaScript library that shows office documents created by KO GmbH. It was started by Jos van den Oever at KO and is now developed by a growing team including external collaborators. It makes it easy to add Open Document Format (ODF) support to your website and to your mobile or desktop applications. It uses HTML and CSS to display ODF documents.
Visit project website

Download or fork now


Download now (see instructions), or fork the code at GitHub and send us a pull request.

Download Source code

ViewerJS was brought to you by KO GmbH | Impressum