glTF File Format (.gltf)

A glTF file is a JSON scene description, developed by the Khronos Group and first released in 2015, that lists a model's meshes, PBR materials, animations and scene hierarchy while its binary geometry and textures sit alongside it in separate buffer and image files.

.gltf3D Models

glTF at a glance#

Full name	GL Transmission Format
File extension	.gltf
Category	3D Models
Developer	Khronos Group
First released	2015
MIME types	model/gltf+json
Compression	Varies from file to file
Specification	glTF 2.0
FileFlip support	FileFlip reads and writes this format

What a .gltf file can hold#

These are the things a glTF file either supports or does not, and they are what decides whether a conversion keeps everything or quietly drops something.

Embedded metadata	Yes
Textures and materials	Yes
Skeletons and animation	Yes
Human readable	Yes

Strengths and limitations of glTF#

What glTF does well

Openly standardised and royalty-free, and an ISO standard (ISO/IEC 12113) since 2022
Physically based materials are part of the core spec, so metallic-roughness surfaces render consistently across compliant viewers
Draco and meshopt extensions can compress geometry substantially for delivery over the web

Where glTF falls short

The JSON form references separate .bin buffers and image files, so a single export is really several files
No native support for NURBS or construction history, since it targets rendering rather than editing
Extensions vendors add for specific material or lighting features are only as interoperable as the viewers that implement them

Use glTF's JSON form when a pipeline needs to inspect or hand-edit the scene structure directly, since it's plain, indexed JSON.

Convert glTF to GLB when the model needs to travel or load as a single file instead of a folder of JSON, buffers and textures.

How to open a .gltf file#

A .gltf file opens in the programs below, grouped by the platform you are on. If you would rather not install anything, FileFlip converts glTF into a format your machine already opens, and it does it in the browser tab rather than on a server.

Platform	Programs that open it
Windows	3D Viewer, Blender
macOS	Blender
Linux	Blender
Web	FileFlip, Babylon.js Sandbox, glTF Viewer

glTF questions people ask#

What's the difference between glTF and GLB?

glTF is a JSON text file that references its geometry buffers and textures as separate files, while GLB packs that same JSON, the buffers and the textures into a single binary file. Both describe the identical data model; GLB just bundles everything one file needs to travel as one upload.

Why does my glTF file come with extra .bin and image files?

A .gltf file is only the JSON description of a scene, meshes, materials and animations; the actual vertex data lives in one or more .bin buffer files and textures are separate image files that the JSON references by path. Losing any of those files leaves the model with missing geometry or textures, which is why glTF exports usually come as a folder or ZIP rather than a single file.

Is glTF free to use?

Yes, glTF is a royalty-free open standard published by the Khronos Group, with no licensing fee to implement a reader or writer for it. It became an ISO standard (ISO/IEC 12113:2022) in 2022, which is part of why so many engines and viewers support it.

Can glTF store animation?

Yes, glTF's core specification includes keyframed animation and skeletal skinning alongside meshes and materials, which is part of why it replaced COLLADA as the standard for delivering animated 3D content over the web.

Converting glTF files#

Convert glTF to another format

Every conversion runs inside your browser. The file is read from your disk, the work happens on your own machine, and nothing is uploaded. How FileFlip works names the engine behind each family and how to verify that for yourself.