Blog · Format comparisons

GLB vs glTF — which should you ship?

Last updated 11 June 2026

GLB and glTF are not really competing formats — they are the same format with different packaging. glTF is the underlying spec from the Khronos Group; GLB is a binary container that bundles everything into one file. The decision is almost always "GLB unless you have a reason." Here's what those reasons are.

Quick comparison

What they actually are

The glTF specification defines a runtime asset format for 3D scenes — meshes, materials, animations, skeletons, scene hierarchy. It does not by itself prescribe how the bytes are stored on disk. Two storage layouts are defined.

.gltf is a JSON manifest that describes the scene and references the binary geometry (a .bin file) and the texture image files (.png, .jpg, .ktx2) as external URIs. Opening a .gltf in a text editor shows readable JSON.

.glb packs the same JSON manifest, the binary buffer, and all the textures into a single binary file with a 12-byte header and chunk markers. A 1-line summary: GLB is "glTF, zipped flat into one file."

Both formats round-trip losslessly. Converting GLB to glTF and back produces identical scene content.

Why GLB wins almost everywhere

One file, one request

A glTF model with separate buffer and 12 textures requires 14 HTTP requests to download. A GLB needs one. For web delivery this is the difference between a snappy load and a flaky one — every extra request adds connection overhead and risks a partial failure.

Shareability

Email, message, drag-and-drop, upload-to-platform — these all assume one file. A glTF "model" that is really 14 files needs to be zipped to travel, and the recipient needs to unzip it before opening. GLB just works.

Smaller, on average

GLB stores binary data as raw bytes. glTF that embeds binary data in the JSON manifest must base64-encode it, which inflates by ~33%. Even non-embedded glTF has per-file overhead.

It's what the ecosystem expects

Almost every web 3D viewer, AR Quick Look, Scene Viewer on Android, Sketchfab embeds, Facebook 3D posts — they all accept GLB. Some accept glTF too, but GLB is the universal default.

Why glTF still has a place

Human-readable manifest

When something is wrong with a model — material that won't render, animation that misbehaves, missing UV channel — being able to open the .gltf JSON in a text editor and read the scene graph is enormously useful. You can grep for material names, find the broken node, see exactly which buffer view is referenced.

Version control

Git handles plain-text glTF JSON cleanly. Binary GLB files are opaque blobs to git and you cannot meaningfully diff them. Studios that store source models in version control often keep authoring files as glTF and ship GLB.

Texture swap workflows

Because textures live as separate image files in a glTF setup, you can swap a normal map or albedo by replacing the image file without touching the model itself. With GLB you have to repack the entire file.

Streaming and partial loading

Some advanced loaders fetch the .gltf manifest first, decide which textures and meshes are needed, and only request those. GLB is all-or-nothing — you cannot start parsing until at least the manifest chunk has arrived, and most loaders wait for the full file before rendering.

Compression — the same in both

Both GLB and glTF can use the same compression extensions: Draco for geometry (typically 8–12x reduction), KTX2/Basis for textures (50–80% smaller than PNG with GPU-native decoding), and Meshopt as an alternative geometry compression with faster decode. The extension is set in the manifest and the compressed payload is in the binary buffer. Neither container has a compression advantage over the other.

Tooling that matters

• glTF-Transform — Node.js library and CLI that converts freely between GLB and glTF, applies Draco/KTX2, inspects, optimises. The de facto Swiss Army knife.
• Blender exports either; defaults to GLB.
• Three.js GLTFLoader reads both with the same loader.
• model-viewer web component accepts both via the src attribute.

The recommendation

For end-user delivery (web, mobile, AR, sharing): always GLB. One file, smaller, universally supported.

For authoring and version control: glTF. Easier to inspect, easier to diff, easier to swap textures without re-exporting.

For converting between the two: glTF-Transform. One command in either direction with zero quality loss.