What is a .glb file?

glTF vs GLB: the difference is packaging

glTF describes a 3D asset; GLB is its binary container. A .gltf is JSON that may reference companion files or embed data. A GLB can put the scene description and geometry into one file. The underlying format does not become more detailed simply because the extension changes. Both use metres for linear distances. Khronos specifies the two encodings.

Choose the package the receiving application expects. For this site's single-file viewer, use a GLB with embedded geometry or a glTF with embedded buffers. It cannot load a separate .bin from your computer just because the JSON names it.

The glTF to GLB converter processes the geometry and other features this site supports. It is not a full asset-packaging tool for textured or animated scenes. Keep the original export for its textures and animation.

Why glTF exists

Khronos designed glTF as "the JPEG of 3D": a format optimised for delivery and display, not for authoring. Geometry is stored the way a GPU wants it, as vertex buffers and index buffers ready to upload, so a viewer can put it on screen without restructuring anything. That is why GLB files load fast in a browser and why every web 3D viewer, AR platform and asset marketplace has standardised on them.

Materials, and what they mean

glTF uses physically based rendering: a base colour, a metallic factor, a roughness factor, and optional normal, occlusion and emissive maps. This is the same material model Blender, Unreal, Unity and Substance use, so appearance transfers across those tools with unusual fidelity.

For engineering work most of that is irrelevant, since you want the shape, but the base colour does carry part identity through a conversion, and this site preserves it.

The unit question

glTF is defined in metres. The specification says so. The file does not, because there is no unit field to read.

That distinction matters more than it sounds. A format that *declares* its unit, like STEP or 3MF, tells you what a file means. glTF fixes the unit globally instead, so a file whose author worked in millimetres and exported without scaling is simply wrong by a factor of 1000, and nothing in the file reveals it.

This site reads glTF as metres, labels that unit as assumed, and scales correctly when converting to a millimetre-based format. A 10 m part becomes a 10,000 mm STL.

What glTF stores well

• A real node hierarchy with transforms, so assemblies survive
• Instancing: one mesh referenced from many nodes
• PBR materials and textures
• Animation, skinning and morph targets
• Cameras and lights

What it does not

• No exact geometry. Everything is triangles. There is no cylinder, only a

faceted approximation of one.

• No parametric history, no feature tree, no tolerances.
• No manufacturing metadata of any kind.

Compressed glTF

Two extensions shrink files considerably: Draco mesh compression and meshopt. Both require a decoder the viewer must ship. This site does not bundle either, and says so if you upload a file that needs one, instead of showing an empty scene. Re-export without compression and it will open.

When to use GLB

• Showing a model on the web or in AR on Android
• Sending someone a model to *look at*, in one file, with colour
• Feeding a rendering or game pipeline

When not to

Anything being manufactured. Send STEP for machining, 3MF or STL for printing.