impress/impress.js

Choose this fork only if substep navigation is the specific feature you want and you are comfortable with a stale, old impress.js branch. For most adopters, upstream is the safer base unless they need this exact interaction model.

Prefer this fork only if Arabic/RTL presentation support is the main requirement. Otherwise, upstream is the better choice because it is far newer, more maintained, and likely has broader compatibility and plugin support.

Choose the upstream project instead unless you specifically need this exact older snapshot. This fork does not show fork-specific features and is materially behind upstream, so it is mainly useful as a frozen baseline rather than a better-maintained alternative.