Khronos glTF (GL Transmission Format) is an open royalty-free specification maintained by the Khronos Group that defines a JSON-based container format for 3D scenes and models, designed for efficient runtime delivery and rendering rather than authoring — storing geometry as compact binary buffer views, referencing PBR (Physically Based Rendering) material parameters, animation data, skeletal hierarchies, and scene graphs in a format that maps closely to GPU resource layouts, minimising parse and upload overhead. glTF 2.0 (2017) established the core specification and is widely regarded as the ‘JPEG of 3D’ due to its adoption across web browsers (via Three.js and Babylon.js), game engines (Unreal, Unity, Godot), AR/VR runtimes (OpenXR, WebXR), and digital twin platforms.
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- The Khronos Group began developing the GL Transmission Format in 2012 as a response to the fragmentation of 3D asset interchange formats: COLLADA (a verbose XML format designed for comprehensive scene representation) had become the de facto standard but was criticised for slow parsing and inconsistent implementation across tools. The design goal for glTF was explicitly runtime efficiency rather than completeness — produce a format whose binary representation can be uploaded directly to GPU buffers with minimal transformation. glTF 1.0 was released in 2015 and glTF 2.0 in June 2017; the latter introduced a standardised PBR metallic-roughness material model and became the target for broad industry adoption.
- The technical architecture of glTF 2.0 centres on a JSON descriptor file (.gltf) that references binary buffer objects (.bin files) containing vertex data, index data, and animation keyframes stored in typed array layouts matching WebGL and Vulkan buffer formats. Textures are stored as PNG or JPEG images (or KTX2 compressed textures with the KHR_texture_basisu extension). The extension system — a catalogue of Khronos-registered and vendor-contributed extensions — allows the core format to be augmented with capabilities such as mesh compression (KHR_mesh_quantization, EXT_meshopt_compression), transmission (KHR_materials_transmission for glass and liquid shaders), XMP metadata embedding, and instanced rendering. The GLB binary container format wraps the JSON and all resources into a single-file archive for convenient distribution.
- The significance of glTF is that it resolved a long-standing fragmentation problem in 3D content pipelines: prior to its adoption, studios, game developers, and web developers maintained separate asset pipelines for FBX (Autodesk’s proprietary format), OBJ (legacy wavefront format), and COLLADA, with lossy conversion steps between them. glTF’s open, royalty-free specification allowed a single export from a DCC tool (Blender, Substance Painter, Cinema 4D) to be consumed without transformation by Three.js, Babylon.js, Unity, Unreal Engine, Godot, iOS RealityKit, Android SceneView, and WebXR applications. The Metaverse Standards Forum has designated glTF as the primary 3D asset format for interoperable metaverse content, and NVIDIA’s USD (Universal Scene Description) format can be bidirectionally converted with glTF for pipeline integration.
- In 2024-2025, the glTF ecosystem continues to expand with extensions addressing emerging needs: KHR_animation_pointer for animating arbitrary JSON properties, EXT_procedural_texture_shaders for WebGPU-compatible material functions, and OMI_physics_body for encoding rigid-body physics parameters. The format is being adopted in industrial IoT digital twin platforms, medical visualisation, and e-commerce 3D product display (WebXR product viewers). Khronos has established the 3D Commerce working group to standardise glTF material fidelity for retail applications. The ongoing challenge is accommodating the semantic richness required for metaverse scene graphs — spatial audio, interaction triggers, access control metadata — without abandoning the format’s runtime efficiency founding principle.