Universal Scene Description
From Just Solve the File Format Problem
Universal Scene Description is a framework developed by Pixar. Also known as Crate files. "It is a system for encoding scalable, hierarchically organized, static and time-sampled data, for the primary purpose of interchanging and augmenting the data between cooperating digital content creation applications."[1][2]
File Identification
USDA files are plain ascii, while USDC are binary files. USDZ is a container for the format in a ZIP structure, used by Apple for 3D and AR applications[3].
USD & USDA files are text files and begin with the ascii #usda 1.0
USDC are binary files and begin with the hex values 5058522D55534443
or PXR-USDC
in ascii.