.skp

Three-dimensional model created by SketchUp software, an easy-to-use 3D design program; allows conceptual designs to be created, viewed, and shared quickly and easily; models created with SketchUp can placed within Google Earth or shared using the 3D Warehouse feature.

SketchUp was originally developed by @Last Software, but was bought by Google in 2006. SketchUp 5 was the last version released by @Last. Version 6 was developed by Google.

Important: SketchUp, originally developed by Google, is now owned by Trimble.