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In 2017, the team behind Pale Moon began the Unified XUL Platform (UXP) project. Add-on support remained almost entirely unchanged, with a slight reduction of Jetpack compatibility. Pale Moon 27 was a major re-fork of the core browser code to Firefox 38 ESR, which added HTTP/2, DirectX 11, MSE/ DASH, and JavaScript ES6 capabilities.
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Starting with version 25, Pale Moon uses a completely independent versioning scheme. Eventually the scope of the project grew, and version 24 became a true fork of Firefox 24 ESR. Straver's first official release of Pale Moon, in 2009, was a rebuild of Firefox 3.5.2 with tweaked compiler settings. Straver is the project founder and lead developer. 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. However, a contributed build for Linux is available that supports some older processors. The official releases do not support older processors without the SSE2 instruction set. The final version for Snow Leopard is the foundation for the Arctic Fox web browser. The end of XP support was quickly followed by Pale Moon getting at least two forks of its own, both of which take the most recent Pale Moon code and recompile it for XP New Moon by roytam1, and Mypal by Feodor2. Version 27.9.4 was the final official release to support Windows Vista as well as the final unofficial release for Mac OS X 10.6 Snow Leopard. Version 26.5 was the final official release to support Windows XP. 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.These include retention of "Complete Themes", themes which apply to the entire UI of the browser rather than affecting only a few elements, support for which was removed in Firefox. Supports add-ons exclusive to Pale Moon, including dozens of themes.Continues add-on support for XUL, XPCOM, and NPAPI plugins, all of which are no longer supported in Firefox.Uses the pre-Australis Firefox user interface.Replaces the Gecko browser engine with the Goanna fork.Always runs in single- process mode, whereas Firefox became a multi-process program.Pale Moon has diverged from Firefox in a number of ways:
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