Readium SDK & JS

These are the two original projects of the Readium Foundation and both are still on active maintenance by the Readium community, a community in which EDRLab plays a large part since its creation in 2015.

What is ReadiumJS?

ReadiumJS is a JavaScript library (readium-js) and viewer (readium-js-viewer) for EPUB 3 rendering, optimized for use on websites in browser-based “cloud” readers. Using ReadiumJS does not require any server-side infrastructure or browser plug-ins. ReadiumJS shares common JS modules (readium-shared-js) with the Readium SDK which targets native apps.

There are two parts to ReadiumJS:

  • A Readium Chrome Extension which is available from the Chrome Web Store. It is one of the most full-featured EPUB 3 Reading Systems available.
  • A cross-browser (as opposed to a Chrome Extension) implementation (known as the CloudReader) based on essentially the same sources but with a different viewer/application front end.

In addition, all of the source code for both the Chrome Extension and the CloudReader can be downloaded from github as source code and modified to suit.

More information about ReadiumJS can be found on the Readium documentation website.

All of the ReadiumJS sub-projects are available under a BSD-type open source license.

What is the Readium SDK?

The Readium SDK project is developing a compact, performant EPUB 3 rendering engine optimized for use in native apps for tablets and other devices. The Readium SDK Core C++ library is cross-platform and implemented largely in native code with some JavaScript/Java/C# implementations where appropriate. It comes along with iOS and Android testing wrappers, called “launchers”.

Note that the Readium SDK Core C++ library was until 2018 dual-licensed: publicly via a Gnu Affero General Public License Version 3, and via an alternative license which provided rights targeted to commercial adopters.

From version 0.30, this dual license has been replaced by a BSD-type license, which allows the use of the SDK in both open and closed-source for free.

Important notice: maintaining this project up-to-date will depend primarily on voluntary developer contributions and the payments of optional Readium SDK maintenance fee by developers relying on this software for their reading applications. 

What is the development status of Readium SDK & JS?

The open-source community is maintaining the Readium codebase on the Readium Github, and the release history is maintained on the Readium documentation website.

The project management and a large part of the maintenance of the software is done by consultants paid by the Readium Foundation. In order to keep this project alive, a yearly financial help is requested from the companies that use Readium in their reading apps.

In March 2018, the current stable version of Readium (both SDK and JS) is 0.30

More information on how to contribute to the development can be found here.

Other Readium projects


The major evolution of the Readium SDK codebase, the objectives being better performances and stability, clarity of source code and documentation.

Discover Readium-2

woman in library reading at a tablet with lock in her hand

Readium LCP

The vendor-neutral and interoperableDigital Rights Management technology, embeddable in any reading application based on the Readium SDK.

Discover Readium LCP

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