A RESS file is a 3D model archive used by games that use the Unity 3D graphics engine. It contains game resource files, such as assets, textures, and materials for 3D models. RESS files are similar to .ASSET files but are not encrypted and have no header.

RESS files are typically found accompanying ASSET files in the data folders of a game installation. You will most likely never come across a RESS file unless you are attempting to edit the resource files in the RESS file to modify gameplay. You can use Unity Assets Explorer and Unity Assets Bundle Extractor (version 2.1_b and later) to open RESS files. NOTE: RESS files commonly appear with the ".resS" extension.