GLB

GLB is the binary container format for the glTF 2.0 asset exchange specification developed by the Khronos Group. It packages a complete 3D model or scene into a single file, including geometry, materials, textures, animations, and the scene graph. GLB is designed to be compact and easy to load, offering a self-contained alternative to the JSON-based glTF plus separate binary and image files.

A GLB file has a fixed header and one or more data chunks. The common arrangement includes a JSON chunk that describes the asset (meshes, materials, textures, animations, and nodes) and a binary (BIN) chunk that stores the actual data referenced by the JSON, such as vertex attributes, indices, and image data. Textures and images are typically stored as binary data within the BIN chunk and referenced by the JSON, allowing the entire asset to be loaded from a single file.

GLB serves as a widely adopted interchange format for 3D content, particularly for web and mobile applications. It is supported by major rendering engines and tools, including Three.js, Babylon.js, Unity, Unreal Engine, Blender, and many online viewers. The single-file packaging simplifies asset management, deployment, and streaming in compatible environments.

Extensions and compression: GLB leverages the glTF extension mechanism to reduce file size and expand capabilities. Notable extensions include KHR_draco_mesh_compression for mesh data and KHR_texture_basisu for compressed textures, among others. These extensions enable smaller GLB files while preserving visual fidelity when supported by the target platform.

Limitations: GLB files can still be large if textures or detailed geometry are used. Some older software may have limited support for the latest glTF or GLB features, and certain advanced features may rely on extensions that must be supported by the consuming application.