For reading GLTF/GLB file system access can be controlled by defining TINYGLTF_NO_FS and providing the necessary callback functions.

Writing GLTF/GLB files seems to be missing this functionality. Even when TINYGLTF_NO_FS is defined, certain functions using std::ofstream are still active (e.g. WriteGltfFile).

Side note: if TINYGLTF_NO_FS is defined, <fstream> is not included. However, it still compiles on most platforms successfully as std::ofstream is pulled in transitively.