


Moonchild Productions develops UXP alongside Pale Moon. It includes the Goanna layout and rendering engine, a fork of Mozilla's Gecko engine. Pale Moon is built upon the Unified XUL Platform (UXP), a cross-platform, multimedia application base with ancestry in Mozilla code. The official releases do not support older processors without the SSE2 instruction set. Pale Moon 27.9.4 was the last release to officially support Windows Vista as well as the final community-contributed release for Mac OS X 10.6 Snow Leopard. Two speciality builds continued to support XP for some time: PM4XP, which was discontinued after release 25.7.0, and a special build intended for devices with Intel Atom processors, which was discontinued with the release of Pale Moon 27.0.0. Official support for Windows XP ended with Pale Moon 25.0.0. The name and logo are trademarked by the project founder and cannot be used without his prior permission.

To ensure quality, redistribution of officially branded Pale Moon binaries is only permissible under specific circumstances.

Pale Moon's source code is released under the Mozilla Public License 2.0 except for parts relating to branding. Uses the IP-API service instead of Google's for geolocation.Defaults to DuckDuckGo as the search engine instead of Google or Yahoo!.Defaults to a customizable start page in cooperation with.Always runs in single- process mode, whereas Firefox became a multi-process program.Replaces the Gecko browser engine with the Goanna fork.Supports NPAPI plugins indiscriminately, all of which are no longer supported by Firefox.Firefox no longer supports this and retains limited options for UI customization. Supports "Complete Themes", add-ons which can customize the entire UI of the browser.Supports extensions built with XUL and XPCOM, which are no longer supported by Firefox.Uses the pre-Australis user interface ("Strata") as carried by Firefox during versions 4-28.Pale Moon has diverged from Firefox in a number of ways:
