Skin or theme file used by Rainmeter, a desktop customization platform used to run desktop applets similar to widgets for Mac OS X or gadgets for the Windows Sidebar; stores a Zip archive of applet images, fonts, metadata, and compiled program code; commonly used for applying themes to the desktop, and adding weather and news reports, clocks, small games, and system performance tools.

RMSKIN files contain five directories the skin content: Addons, Fonts, Plugins, Skins, and Themes. They also contain a ".cfg" file in the root directory which contains metadata, such as the name, author, and version. Since RMSKIN files are compressed .ZIP files, you can rename their extension to ".zip" and decompress them with any Zip decompression utility. You can also create them by compressing a ZIP file and renaming the extension to ".rmskin."