glTF (GL Transmission Format) is an open standard file format for 3D scenes and models, developed by the Khronos Group. A glTF file uses JSON to describe the scene structure and references external binary files for geometry and textures. This separation allows for efficient parsing and loading, making it the de facto standard for 3D on the web. Sample glTF files are used to test the flexibility of 3D rendering engines. Developers use them to ensure that the JSON structure is parsed correctly and that external resource requests are handled efficiently. They are also used to test advanced features like morph targets, skinning, and multiple texture sets in a web-based environment.