Pale Moon

Pale Moon is a free and open-source web browser licensed under the MPL-2.0 with an emphasis on customization. There are official releases for Microsoft Windows, FreeBSD, macOS, and Linux.

Pale Moon originated as a fork of Firefox, but has subsequently diverged. The main differences are the user interface, add-on support, and running in single-process mode. Pale Moon retains the user interface of Firefox from versions 4 to 28 and supports legacy Firefox add-ons.

Its motto is "Your browser, Your way."

Features

Pale Moon's default user interface is the one that was used by Firefox from versions 4 to 28, known as Strata. It always runs in single process mode and uses a rendering engine known as Goanna. The browser has its own set of extensions and supports legacy Firefox add-ons built with XUL and XPCOM, which Firefox dropped support for in 2017 with version 57. NPAPI plugins, such as Adobe Flash Player, are also supported. The browser's entire user interface can be customized by complete themes and lightweight themes are also available. Pale Moon's default search engine is DuckDuckGo and it uses the IP-API service instead of Google for geolocation. The browser is known to be lightweight on resource usage.

Pale Moon has no telemetry or data collection.

Unified XUL Platform (UXP)

Pale Moon is built upon the Unified XUL Platform (UXP), a cross-platform, multimedia application base that was forked from Mozilla code prior to the introduction of Firefox Quantum. UXP is a fork of the Firefox 52 ESR platform that was created in 2017 due to XUL/XPCOM support being removed from the Firefox codebase. It includes the Goanna layout and rendering engine, a fork of Mozilla's Gecko engine. Moonchild Productions develops UXP independently alongside Pale Moon.