glTF Viewer for .gltf and .glb Files

A .gltf is a JSON text file you can open in any code editor. It lists the scene's nodes with their names and transforms, the meshes they point to, the PBR materials and textures, and any animations. The heavy data, meaning vertex positions, normals, UVs and triangle indices, is not written as readable text. It sits in binary buffers that the JSON refers to by URI.

That URI decides whether a viewer can open the file on its own. It can be a data URI that holds the buffer as base64 text, which makes the .gltf self-contained, or a file name such as scene.bin, which means the .gltf needs the files saved next to it. A .glb is the same structure packed into one binary file.

A web page only sees the files you choose, and this viewer reads each file on its own, so it cannot follow a link from scene.gltf to scene.bin. A .gltf like that shows a message saying it points to separate files. Nothing is wrong with the model; it only needs packing into one file.

To pack it, open the .gltf in Blender with File > Import > glTF 2.0 and export it again with Format set to glTF Binary (.glb). On Sketchfab, choose the GLB download instead of the glTF zip. On the command line, the glTF Transform CLI does the same job with gltf-transform copy scene.gltf scene.glb.

With Show original materials on, the scene is drawn with its glTF PBR materials: base color, metalness, roughness and any textures stored in the file. Turn it off and every mesh merges into one plain surface, which is how a slicer and an STL file see the model.

If a .gltf has its geometry embedded but points to texture images saved beside it, the model still opens with its material colors, just without those images. That is enough to check shape and size. For a faithful preview, pack the textures into a .glb.

glTF measures everything in meters with Y pointing up. The viewer converts to millimeters, or inches with the toggle under the preview, turns the model Z-up and sets it on a build plate, so the numbers match what a slicer would report.

That makes unit mistakes easy to spot. A model that reads around 2000 mm was built at life size or as a normalized AI model, which is normal for a game scene but needs resizing before printing. A small part that reads 50000 mm was probably exported from millimeters without conversion, and is worth exporting again with the right unit settings.

The triangle count is the quick budget check. Phones and browsers render lean meshes fastest, while AI generated and photogrammetry models often carry far more triangles than they need, so a high count is a hint to decimate or compress before you ship.

The object count shows how the scene is split. A prop made of one or two meshes is easy to place and reuse, while dozens of tiny meshes add draw calls in a game engine. The wireframe view shows where the triangles are concentrated.