What is the GLB file format?
.glb is the binary container form of the .gltf format (GL Transmission Format), developed and maintained by the Khronos Group. Where a .gltf file is plain JSON that references external .bin geometry files and separate image assets, a .glb file bundles everything - the scene graph JSON, binary geometry and animation buffers, and embedded textures - into a single self-contained file.
The file begins with a 12-byte little-endian header: the ASCII magic string glTF (hex 67 6C 54 46), a uint32 version field (value 2 for glTF 2.0), and a uint32 total file length. Following the header are length-prefixed chunks: a JSON chunk carrying the scene description (nodes, materials, cameras, animations) and a BIN\ chunk holding the raw binary buffer data.
.glb is sometimes called "the JPEG of 3D" because of its compact size, broad support and suitability for web delivery. It is the default asset format for AR on Android via Scene Viewer and the <model-viewer> web component, and is widely used in WebGL engines such as three.js and Babylon.js. Compared to .fbx or .obj, it is purpose-built for real-time rendering with physically based materials baked in.
Optional Khronos extensions add Draco mesh compression (KHR_draco_mesh_compression) and KTX2/Basis Universal texture compression (KHR_texture_basisu), significantly reducing file sizes for large scenes.
Security & safety
RISK: LOWA GLB is 3D data, not an executable, so opening one to view it is safe. Realistic cautions are non-malicious: very high-poly scans or 4K textures can be heavy to load, and historically there have been parser vulnerabilities in some glTF/GLB loaders - keep your 3D software and browser-based viewers up to date and import models from reputable sources. As always, verify the real extension: a file disguised as "model.glb" that is actually an executable is the real risk, not the GLB format itself.
Format details
in a nutshell- Raptor: Call of the Shadows support file - A legacy data file for the 1994 DOS game Raptor; the source database mislabels this as the primary meaning of .glb, but it is obsolete and unrelated to the dominant glTF Binary format.
- Analytical Graphics STK globe/data file - An older GIS/STK auxiliary file; very niche compared with the 3D glTF Binary meaning.
Programs that open GLB files
Windows3 apps
Blender
Open-source File > Import > glTF 2.0 (.glb/.gltf) to view and fully edit geometry, materials and animation. The free standard 3D tool. 
3D Viewer (Microsoft)
Free Double-click the .glb to view, rotate and inspect the model; the free Microsoft Store app reads GLB/glTF natively. View-only.
Babylon.js Sandbox
Free Drag the .glb into the browser page to view materials, animations and the scene tree - no install. 
macOS2 apps
Quick Look / Preview
Built-in Press Space on a .glb in Finder, or open in Preview; recent macOS renders glTF/GLB directly. View-only. 
Linux2 apps
gltf-viewer (donmccurdy)
Open-source Open in any browser and drag the .glb in to view with PBR materials and animation. 
Android1 app
Scene Viewer / model-viewer
Free GLB is the native AR format on Android - open via a <model-viewer> link or Scene Viewer to place it in AR.
Reality Converter / Quick Look (via USDZ)
Free iOS AR Quick Look uses USDZ - use Apple's Reality Converter or an online tool to convert GLB to USDZ, then open in Quick Look.
gltf-viewer (donmccurdy)
Open-source Drag the .glb into the page to view, inspect materials and play animations. Technical details
deep spec| File magic (signature) | ASCII "glTF" at byte offset 0 (hex: 67 6C 54 46) |
| Byte order | Little-endian throughout |
| Header size | 12 bytes: 4-byte magic + uint32 version (value 2) + uint32 total file length |
| Chunk structure | JSON chunk (type 0x4E4F534A) followed by BIN chunk (type 0x004E4942); each prefixed with uint32 chunk length and uint32 chunk type |
| MIME type | model/gltf-binary (also served as application/octet-stream) |
| Encoding | Binary container wrapping UTF-8 JSON scene description + raw binary geometry/animation buffers |
| Compression | None by default; optional Draco mesh compression via KHR_draco_mesh_compression and KTX2/Basis Universal textures via KHR_texture_basisu |
| PBR material model | Physically based metallic-roughness shading defined in the JSON chunk; specular-glossiness via KHR_materials_specular |
| Animation support | Keyframe animations for translation, rotation, scale and morph-target weights; skeletal/skin animation via joint hierarchies |
| Texture color depth | 8 bpc (24-bit RGB or 32-bit RGBA via embedded JPEG or PNG); HDR environment maps via extensions |
| Texture size limit | No format-imposed limit; GPU-bound in practice (commonly up to 8192×8192 per texture) |
| Self-containment | All geometry, textures, animations and scene graph bundled in one file; no external dependencies unlike .gltf + .bin + image files |
| Version field | uint32 in GLB header identifies glTF 2.0 (value 2); asset.version = "2.0" also present inside the JSON chunk |
| Typical file size | 50 KB - 100 MB; most web and AR assets fall in the 1-30 MB range |
| Platform support | Windows, macOS, Linux, Android, iOS and Web (WebGL via three.js, Babylon.js, model-viewer) |
| Encryption / integrity | No built-in encryption or checksum; total-length field in header only |
| Released | 2017 (glTF 2.0; GLB binary container) |
| Latest version | glTF 2.0 (GLB container, ratified by Khronos; ongoing extensions e.g. KHR_materials_*) |
| Open standard | Yes · royalty-free |
| Specification | registry.khronos.org |
GLB conversions
Community Q&A
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