Overview
Waterfox is a free and open-source web browser and fork of Firefox. It claims to be ethical and user-centric, emphasizing performance and privacy. There are official Waterfox releases for Windows, macOS, and Linux. It was initially created to provide official 64-bit support, back when Firefox was only available for 32-bit systems.
Divisions
Waterfox
Waterfox shares core features and technologies like the Gecko browser engine and support for Firefox Add-ons with Firefox. It is also compatible with Google Chrome and Opera extensions. It disables telemetry and Pocket by default, which are present in Firefox builds. However, it collects technical information about the user's device to update properly.
Waterfox Classic
Waterfox Classic is a version of the browser based on an older version of the Gecko engine that supports legacy XUL and XPCOM add-on capabilities that Firefox removed in version 57. It is still partially maintained with fixes and patches from Waterfox and Firefox ESR releases. However, its development has been separated due to several changes from Waterfox that are otherwise unapplicable.
From Wikipedia (CC BY-SA 4.0).