GLB vs glTF When to Use Which

The Khronos Group created glTF (GL Transmission Format) as a universal delivery format for 3D content. Version 2.0 was released in June 2017 and later adopted as international standard ISO/IEC 12113:2022 in July 2022. It is often called "the JPEG of 3D" because it fills the same role for 3D models that JPEG fills for images: a compact, open format that works everywhere.

glTF 2.0 uses physically based rendering (PBR) materials. The same material definition renders correctly whether you are using WebGL, Vulkan, Metal, or Direct3D. The earlier 1.0 version relied on raw GLSL shaders, tying models to a single rendering API. That limitation is why glTF 1.0 is effectively obsolete today.

A standard glTF file set has three parts:

• A .gltf file with the scene description as readable JSON
• A .bin file with raw geometry, animation, and skin data
• External image files (.png, .jpg) for textures

This separation makes the format easy to work with. You can open the .gltf file in any text editor, inspect the node hierarchy, check material properties, and make quick edits by hand.

GLB packages everything into one file. The JSON scene description, binary mesh data, and texture images all go into a single .glb file.

The file starts with a 12 byte header (a magic number, the version, and the total file size), followed by chunks. The first chunk is always the JSON scene graph. The second chunk holds the binary buffer with geometry, animation data, and embedded textures.

The practical benefit is straightforward: one file to manage, one file to transfer, one file to cache. No missing textures, no broken relative paths, no ZIP archives to coordinate.

GLB files are also smaller than equivalent glTF when textures are involved. A glTF file that embeds textures using base64 data URIs inflates them by roughly 33%. GLB stores the same data as raw binary, skipping that overhead entirely.

GLB is the better choice for most delivery scenarios.

Web applications need fast loading, and a single HTTP request beats multiple requests, especially on mobile connections. Most web viewers, including three.js and <model-viewer>, handle GLB without extra configuration.

E-commerce platforms like Shopify accept GLB for product 3D models. Shopify recommends keeping GLB files under 15 MB for mobile performance, ideally under 5 MB.

Android AR uses GLB as its native format. Google Scene Viewer, available on Android 7.0 and above, loads GLB files directly. The <model-viewer> web component can launch Scene Viewer on compatible Android devices automatically.

Game engines including Unreal Engine specifically recommend GLB as an import format. Unity supports both GLB and glTF through the glTFast package, which serves as the default importer for both file types.

If you are distributing 3D content to end users, GLB is almost always the right pick. It is simpler, smaller, and more portable.

glTF with separate files has clear advantages in development and production workflows.

Debugging and inspection. When something looks wrong with a model, opening the JSON in a text editor to inspect node transforms, material bindings, or buffer references can save significant debugging time. That is not possible with a binary file.

Version control. Teams that track 3D assets in Git benefit from the separate file structure. JSON diffs show exactly what changed in the scene graph. Reviewing a pull request that modifies a GLB file tells you nothing about what actually changed.

Texture reuse. Multiple models can reference the same external texture files. In a project with 50 models sharing a common material atlas, that is 50 fewer duplicate texture copies compared to bundling everything into GLB.

Progressive loading. Web applications can load the geometry first, render a basic model, and then stream textures in the background. This gives users something to see immediately while higher resolution assets continue loading. GLB cannot do this since the entire file loads as one unit.

Both formats support the same compression extensions.

Draco geometry compression (KHR_draco_mesh_compression) can reduce mesh data by 70% to 90% with negligible visual impact. It requires a decoder library at runtime (DRACOLoader in three.js). One limitation: Draco cannot compress morph targets.

meshopt compression (EXT_meshopt_compression) is an alternative that handles morph targets, animations, and all geometry types. It is designed for fast decoding on the GPU.

KTX2 texture compression (KHR_texture_basisu) shrinks texture file sizes and reduces GPU memory usage simultaneously. Textures are transcoded to the device's native GPU format at runtime.

Combining geometry compression with KTX2 textures can cut total file size by 70% to 90% with minimal visual impact. Polyforge supports Draco compression for GLB output, making it easy to shrink your models before distribution.

Where each format is used today:

Apple AR Quick Look on iOS requires USDZ, not glTF or GLB. Models must be converted to USDZ before they will work in iOS AR experiences.

Google Scene Viewer on Android uses GLB natively. The <model-viewer> web component handles the iOS and Android split automatically, serving the right experience for each platform.

Shopify accepts GLB and USDZ, serving the correct format based on the customer's device.

Unity supports both formats through the glTFast package, which registers as the default importer for .gltf and .glb files.

Unreal Engine has built in GLB import support.

Blender exports both glTF and GLB from the same export dialog, with options for Draco compression and separate or embedded output.

Three.js uses a single GLTFLoader for both formats. The loader detects the format automatically from the file header.