GLTF vs GLB — What's the Difference? Which Format for the Web?

If you work with 3D content for the web, AR, or game engines, you've almost certainly encountered both GLTF and GLB files. They're often mentioned interchangeably, and many tools offer both as export options. But they are not the same thing, and choosing the wrong one for your use case can cause headaches ranging from missing textures to bloated load times.

Let's break down exactly what each format is, how they differ under the hood, and when you should reach for one over the other.

What is GLTF?

GLTF (GL Transmission Format) is an open standard developed by the Khronos Group — the same organization behind OpenGL, Vulkan, and WebGL. It's often called the "JPEG of 3D" because it was designed to be a universal, efficient format for transmitting 3D scenes.

A GLTF file is actually a JSON text file with the extension .gltf. This JSON describes the scene graph: nodes, meshes, materials, animations, cameras, and lights. But the JSON alone doesn't contain the heavy data. Instead, it references external files:

• .bin files — binary buffers containing vertex positions, normals, UV coordinates, animation keyframes, and skin weights. This is the raw geometry data.
• Texture images — typically PNG or JPEG files for base color, normal maps, metallic-roughness maps, occlusion, and emissive textures.

So a typical GLTF asset might look like this on disk:

• model.gltf — the JSON scene description (a few KB)
• model.bin — the geometry buffer (a few MB)
• textures/baseColor.png — diffuse texture (varies)
• textures/normal.png — normal map
• textures/metallicRoughness.png — PBR material map

This multi-file structure means GLTF is essentially a folder format. You can't just share a single .gltf file and expect it to work — you need to include all the referenced binaries and textures alongside it.

What is GLB?

GLB (GL Binary) is the binary container variant of GLTF. It takes everything — the JSON, the binary buffers, and all textures — and packs them into a single binary file with the extension .glb.

The GLB file structure is simple: a 12-byte header, followed by a JSON chunk (the same scene description), followed by a binary chunk (all buffers and images concatenated together). The JSON references data within the binary chunk using byte offsets instead of external file paths.

The result is one file that contains everything. No external dependencies. No missing textures. No folder structures to manage.

Key technical differences

File count

This is the most obvious difference. GLTF = multiple files (JSON + .bin + textures). GLB = one file. For web delivery, email attachments, AR experiences, and embedding in applications, a single file is dramatically easier to handle.

File size

GLB files are typically slightly smaller than the equivalent GLTF asset folder. The JSON chunk in GLB is more compact (no base64 encoding needed for inline data), and the binary packing eliminates per-file overhead. However, the difference is usually modest — perhaps 5-15% smaller for texture-heavy models.

There's a catch: GLTF's separate texture files can be individually compressed and cached by web servers and CDNs. If you're serving the same model repeatedly and the geometry changes but textures stay the same, GLTF's multi-file approach lets browsers cache the textures independently. With GLB, any change means re-downloading the entire file.

Editability

GLTF's JSON file is human-readable. You can open it in a text editor and inspect the scene graph, material definitions, and animation data. You can manually adjust material properties, rename nodes, or debug issues without any special tools. This is enormously valuable during development.

GLB is binary. You can't meaningfully edit it in a text editor. To inspect or modify a GLB, you need to convert it back to GLTF first, make your changes, then re-pack it.

Texture handling

GLTF references textures as separate image files (PNG, JPEG, WebP). This means you can swap textures independently, optimize individual images, or use different resolutions for different platforms — all without touching the geometry or scene description.

GLB embeds textures inside the binary blob. Swapping a texture requires unpacking the entire file, replacing the image, and repacking. Tools like gltf-transform make this easier, but it's still more friction than just replacing a PNG file.

PBR materials

Both formats support the same PBR (Physically Based Rendering) material model. GLTF 2.0 uses the metallic-roughness workflow by default, with extensions available for specular-glossiness and other advanced material types. The material definitions are identical in both GLTF and GLB — the only difference is how the texture images are stored (external files vs. embedded blobs).

When to use GLTF

• During development — when you're iterating on materials, adjusting scene hierarchy, or debugging rendering issues. The human-readable JSON makes troubleshooting much faster.
• When textures change independently — if your workflow involves swapping textures frequently (e.g., different color variants of the same product), GLTF's separate files are more convenient.
• For CDN caching optimization — on high-traffic websites serving the same model, GLTF's separate files can be cached independently by the browser and CDN. Texture cache hits avoid re-downloading geometry and vice versa.
• Version control — since the .gltf file is JSON, it diffs cleanly in Git. You can see exactly what changed between commits. Binary .bin files and textures still won't diff well, but the scene structure changes are visible.
• Build pipelines — if you have a build step that processes textures (compression, resizing, format conversion), working with separate files is easier than unpacking and repacking a binary container.

When to use GLB

• Web delivery — one file, one HTTP request. No CORS issues from loading external textures. No broken models from missing files. GLB is the better choice for production web deployment in most cases.
• AR experiences — Apple's Quick Look, Android's Scene Viewer, and WebXR all prefer or require GLB. AR Quick Look on iOS specifically expects a USDZ or GLB file.
• Embedding in applications — game engines, desktop apps, and mobile apps that load 3D models at runtime generally prefer a single self-contained file.
• Sharing and distribution — email a single .glb file, upload it to a platform, or share it in a message. No zip files, no folder structures, no "where's the texture?" questions.
• 3D viewers — online 3D viewers (including GeometryViewer) handle GLB more reliably because there are no external dependencies that might fail to load.

Draco compression

Both GLTF and GLB support Draco mesh compression, a Google-developed algorithm that dramatically reduces geometry data size. Draco can compress vertex positions, normals, and UV coordinates by 80-90%, making file sizes much smaller without visible quality loss.

When Draco compression is applied, the binary buffer contains compressed data that must be decoded at load time. This adds a small decompression step (typically 50-200ms for medium-complexity models), but the reduction in download size usually more than compensates, especially on slow connections.

You can apply Draco compression to either format using tools like gltf-transform, glTF-Pipeline, or Blender's GLTF export options. For web delivery, we strongly recommend it — a 10MB GLB might compress to 2MB with Draco enabled.

Converting between formats

The good news is that GLTF and GLB are fully interconvertible with zero data loss. They contain exactly the same information — just packaged differently. You can convert freely between them:

• Blender — export as either format via File > Export > glTF 2.0
• gltf-transform — command-line tool: gltf-transform copy model.gltf model.glb
• glTF-Pipeline — Cesium's tool: gltf-pipeline -i model.gltf -o model.glb
• Online converters — various web tools handle the conversion, though we recommend offline tools for large files or sensitive models

What about other 3D formats?

GLTF/GLB has largely won the "web 3D format" battle. FBX is still common in game development pipelines. OBJ is still used for simple geometry exchange. USD/USDZ is gaining traction in Apple's ecosystem. But for web-first 3D content, GLTF/GLB is the standard that virtually every engine, viewer, and platform supports.

The bottom line

Use GLTF during development when you need to inspect, edit, and iterate on your 3D assets. The human-readable JSON and separate files make it easier to debug and modify.

Use GLB for delivery when you're shipping to the web, AR, or end users. The single-file format is simpler to serve, share, and embed. Add Draco compression for even smaller files.

And if you're not sure which one you have or need? Just open it in GeometryViewer. Both work exactly the same.