Web experimental releases

We are happy to introduce our new Experimental Release stage. It lets you be a part of the early stages of testing new features and help us improve functionality and polish developer experience.

5.0.0-experimental.2025091601 (2025-09-23)

API Docs

This version has all bugfixes from 4.5.0, but also some additional changes and features from the upcoming 5.0.0.

Note that this experimental release does not include all upcoming changes for 5.0.0, but should be used for evaluating the ContinuousScrollRenderer

Breaking changes

• The minimum supported browser versions have changed:

  • Safari 15

  • Firefox 128

  • Chrome 64

  • Edge 79

• The distributed framework module files .mjs are now real ES modules instead of importing the common JS version of the module.

• The distributed framework module files are now using ECMASCRIPT 2018 syntax.

New features

• Added support for rendering the ReaderView in a Shadow DOM. Previously, our styles were not reaching the viewElement if it was inside a Shadow DOM but that has now been fixed.

• Added a new renderer option swipeNavigationGestureThreshold. This option can be used to configure the swipe distance required to perform a swipe navigation. Additionally, swipe animations have been refined to start more smoothly.

Bugfixes

• Fixed elements incorrectly assigned a tabindex of -1, preventing focus via keyboard navigation.

• Resolved an issue where pages with overflow-x set caused reflowing to break due to browsers implicitly setting overflow-y to auto.

Scroll renderer improvements since 4.4.0-experimental.2025062501

• Several bugs and issues have been fixed.

• The duration of the smooth scrolling can now be controlled with the renderer options scrollAnimationDurationMs and scrollAnimationMaxDistance. Please refer to the API documentation for more information.

4.4.0-experimental.2025062501 (2025-06-30)

API Docs

This version is based on the previously released 4.4.0.

New features

• Added the new renderer ContinuousScrollRenderer that shows all documents in a single vertical scrolling view.

Changes since 4.3.0-experimental.2025050801

• Added a new ReaderView.goTo() option to control how scroll renderers behave when the target position is already visible in the ReaderView.

• Scroll renderers can now smoothly scroll to nearby positions.

• Added a new event, rendererScrollChanged, which is fired continuously while scroll renderers are scrolling.

• Changed the rendererScrollStarted event type to IRendererScrollEngineEvent. It is now possible to determine whether scrolling was initiated by the user by inspecting the userGenerated property.

• Fixed several bugs and issues in the ContinuousScrollRenderer.

4.3.0-experimental.2025050801 (2025-05-08)

API Docs

This version is based on the previously released 4.3.0.

New features

• Added the new renderer ContinuousScrollRenderer that shows all documents in a single vertical scrolling view.

4.2.1-experimental.2025041101 (2025-04-11)

API Docs

This version is based on the previously released 4.2.1.

New features

• Added the new renderer ContinuousScrollRenderer that shows all documents in a single vertical scrolling view.

4.0.0-experimental.2024062701 (2024-06-27)

API Docs

This version is based on the previously released 4.0.0-rc.1.

New features

• Introduced a new option IEpubContentBlockOptions.attributeNamesThatCreateContentBlocks. With this option, you can specify which element attribute names should trigger the creation of a ContentBlock for an element.