GLB vs glTF: What Is the Difference?

GLB and glTF hold exactly the same 3D data; the difference is packaging, and that decides how easy the file is to edit, host and share.

Updated 20 October 2026 · 6 min read

The short answer to GLB vs glTF: both are the same Khronos glTF 2.0 format. A .gltf file is human-readable JSON that points to separate binary and image files, while a .glb file packs the JSON, geometry and textures into a single binary file. The meshes, materials and animations inside are identical, and you can convert between the two without any loss. This guide explains the structure, when each variant is the better choice, how compression fits in, and how to keep file sizes small for web and AR.

What glTF stores

glTF (GL Transmission Format) was designed as a delivery format for real-time 3D: compact, quick to parse and close to how GPUs consume data. A glTF 2.0 asset can contain:

• A scene graph of nodes with translation, rotation and scale.
• Meshes as typed vertex arrays (positions, normals, UVs, tangents, colours) with indices.
• Physically based (PBR) metallic-roughness materials, with optional extensions for clearcoat, transmission, sheen and more.
• Textures (PNG or JPEG in the core spec; KTX2 and WebP via extensions).
• Cameras, skins (skeletons), morph targets and keyframe animations.

By specification, glTF uses metres as the unit and a right-handed coordinate system with +Y up. What it does not try to be is an authoring format: there is no construction history, no NURBS and no editable modifiers.

The unit convention matters when files cross into other tools. A model authored in millimetres but exported without scaling arrives 1,000 times too large in a viewer that trusts the metre convention, and the reverse happens when a GLB goes to a slicer that assumes millimetres. If an object appears tiny or enormous after import, check the scale factor before anything else.

How a .gltf file is structured

A typical "separate" glTF export is three or more files:

• model.gltf – JSON describing nodes, meshes, materials, animations and where the data lives.
• model.bin – raw binary buffers: vertex positions, normals, UVs, indices, animation keyframes.
• textures – image files such as basecolor.png or normal.jpg, referenced by relative path.

There is also an "embedded" variant where buffers and images are stored inside the JSON as base64 data URIs. It is a single file, but base64 inflates binary data by about 33 % and is slower to decode, so it is mostly useful for small test assets.

How a .glb file is structured

GLB is the binary container for the same content. It has a 12-byte header (magic "glTF", version 2, total length), followed by a JSON chunk and an optional BIN chunk holding all buffers and, usually, the images. Because everything sits in one file with no base64 overhead, GLB is about the same size as the separate .gltf + .bin + textures combined, and it can be served, uploaded and cached as one request.

GLB vs glTF compared

When to use glTF (.gltf)

• During development. You can open the JSON in a text editor and see exactly which materials, nodes and extensions are present – useful when something renders wrong.
• When textures change often. Replace a PNG and reload without re-exporting the whole model.
• When several models share textures. Multiple .gltf files can reference the same image, so a browser downloads it once.
• In version control. JSON diffs are readable; binary GLB diffs are not.

When to use GLB

• Publishing on the web. One URL, one HTTP request, no broken relative paths. three.js, Babylon.js and the model-viewer component load GLB directly.
• Android AR. Google's Scene Viewer accepts glTF/GLB; GLB is the practical choice.
• Uploading to platforms. Marketplaces, social and e-commerce platforms commonly ask for a single GLB.
• Sending to someone else. Nothing can get separated or lost in an email or ZIP.

For iPhone and iPad AR Quick Look you need USDZ instead; convert with GLB to USDZ and ship both.

Converting between GLB and glTF

Conversion is lossless in both directions because only the packaging changes:

1. To pack a .gltf with its .bin and textures into one file, use glTF to GLB. Select all the related files together so the references resolve.
2. To unpack a GLB for inspection or texture editing, use GLB to glTF.
3. In Blender, the glTF exporter offers "glTF Binary (.glb)", "glTF Separate (.gltf + .bin + textures)" and, depending on version, "glTF Embedded".
4. On the command line, glTF Transform (gltf-transform copy model.gltf model.glb) and gltfpack both convert and optimise.

To check the result, open it in a GLB viewer or glTF viewer and confirm textures and animations survived.

Draco and meshopt compression

Both GLB and glTF support geometry compression through extensions:

• Draco (KHR_draco_mesh_compression) – Google's mesh codec. It often shrinks geometry by a large factor, sometimes 80–90 % on dense meshes, at the cost of quantisation and decode time. The viewer needs a Draco decoder (a WebAssembly module of a few hundred kilobytes).
• meshopt (EXT_meshopt_compression) – compresses vertex and index data, and also animation data, with a very fast and small decoder. Combined with standard gzip or Brotli on the server, results are often close to Draco with faster decoding.

Both are lossy at the quantisation step. For product visuals that is invisible; for files that will later be converted to STL for printing, keep an uncompressed master. Not every importer supports these extensions, so test the target platform before publishing a compressed file.

File size tips for web and AR

In most real-world GLBs, textures take more space than geometry. Work in this order:

1. Resize textures. 4096×4096 maps are rarely needed on a phone screen. Dropping to 2048 cuts pixel count by 75 %; 1024 is often enough for small products.
2. Use the right image format. JPEG for base colour without transparency, PNG only when you need alpha or lossless data, or KTX2 (Basis Universal) to reduce GPU memory as well as download size.
3. Reduce triangles. A web product model typically looks good at 20,000–100,000 triangles. Scan or CAD exports with millions of triangles should be decimated first.
4. Compress geometry with Draco or meshopt.
5. Remove unused data: hidden objects, unused materials, extra UV sets, empty animations. glTF Transform's prune and dedup commands do this automatically.

A practical target for a product viewer on mobile is a GLB of a few megabytes at most; many well-optimised product models come in under 2–5 MB.

FAQ

Is GLB better than glTF?

Neither is better in quality; they contain the same data. GLB is better for delivery because it is one file, while .gltf is better for editing and debugging because it is readable JSON.

Does converting glTF to GLB lose quality?

No. The geometry, materials, textures and animations are copied unchanged into a binary container. Only compression steps such as Draco or texture resizing are lossy.

Why is my .gltf showing without textures?

The JSON references textures and the .bin file by relative path. If those files were not uploaded or moved together, the viewer cannot find them. Load all files at once or convert to GLB.

Can I 3D print a GLB file?

Yes, after converting to STL or 3MF. Check the scale, since glTF uses metres and slicers assume millimetres, and make sure the mesh is closed.