GLTF explained: viewers, conversions and GLB differences

GLTF stands for GL Transmission Format. GL is short for Graphics Library, a family of standards for 3D graphics. Behind those standards sits the Khronos Group, an international consortium of technology companies. The same group is responsible for both the GLTF standard and WebGL, the technology browsers use to render 3D.

The GLTF standard defines what a 3D model file must contain. From the shape and materials, to optional animations and scene info. Because all tools share those rules, you can build a model in one tool and display it in another without information getting lost.

Version 2.0 of the standard has been stable since 2017. The developers maintain it openly, so anyone can look up the rules or propose improvements. New additions arrive regularly for better quality and smaller files.

The section above was about the GLTF standard. In practice, that standard comes in two file variants, with different extensions and different purposes.

.gltf is split into a text file with the scene info plus separate files for textures and geometry. Because the text file is readable, tools and scripts can inspect and modify its contents. That's why this variant is mainly used while a model is being built and exchanged.

.glb packs everything into a single file. More compact, faster to load and easier to deliver. This is the variant that ends up on a webshop, works in browsers and is suited for AR.

Three routes, depending on what you need.

Five conversions you'll run into in practice.

Rule of thumb: convert everything to GLB for web and AR. Other formats only when tooling demands it.

The GLTF 2.0 spec is maintained at github.com/KhronosGroup/glTF. The main parts are asset info, scenes and nodes for hierarchy, mesh and primitives for geometry. Alongside those: materials, animations, skins and textures.

Where the standard really gets powerful is in the extensions. KHR_draco_mesh_compression for geometry compression. KHR_texture_basisu for KTX2 textures. KHR_materials_transmission, _ior, _sheen and more for advanced PBR materials. EXT_meshopt_compression as an alternative to Draco.

Not every viewer supports every extension. Always validate through the official gltf-validator when you get a file from a supplier. A GLTF with unknown extensions can look fine in your viewer and break in the client's.

In practice you work in GLTF and deliver a GLB. That matches what each variant was built for.

Pick GLTF for the phase where tools and people work together on a model. The text file is readable and inspectable, and separate files are easier in version control because you can see what changes per version.

Pick GLB for the final phase. Compact, single file, ready for production and publication on a webshop or in AR.

In almost every 3D pipeline that's the natural order. GLTF while working, GLB at delivery.

You have a GLTF ready for production or demo. Now you want to serve it to clients or visitors. First, convert the GLTF to a GLB. That's the binary format browsers and hosting platforms deliver. After that, you need a hosting solution that serves the file through a fast CDN, handles the viewer so visitors don't have to install anything, and works on desktop, mobile and in AR.

Virtualdisplay Portal does exactly that. Convert your GLTF to GLB using gltf.report or gltfpack, upload to Portal and you get an embed code. Your first model is free. For 3D artists and developers who want to demo their work to a client or in a project, that's the fastest route.

Want to know more about GLB as a web format? Read our explainer on the GLB file for webshops.