What a GLB file actually is
A GLB is a binary container for a glTF 2.0 scene. It holds the scene description, the binary
buffer that contains vertex data, and usually the images used by the materials. The result is
one file instead of a .gltf plus its .bin and texture folder.
That makes GLB the easy format to download from a marketplace, a Sketchfab model or a real-time engine. It is not a print format: it can carry cameras, lights, skinning, animation and PBR materials, none of which belong in an STL.
What the converter keeps and what it drops
| Data | Result | Why |
|---|---|---|
| Triangles and positions | Kept | Geometry is the part a slicer can print. |
| Node transforms | Applied | Every mesh is baked into world space. |
| Instances | Expanded | Each repeated mesh becomes its own triangles. |
| Materials and textures | Dropped | STL has no material model. |
| Animation, skinning, cameras | Dropped | STL stores static geometry only. |
| Units | Converted only when you ask | STL has no unit field; choose metres → mm when needed. |
How to convert a GLB to STL
- Drop the GLB. Drag a .glb into the converter above, or click the drop zone and choose the file. A GLB is self-contained, so there is no .bin to collect.
- Pick the source unit. glTF is authored in metres by specification. Choose metres → mm when the file follows that convention; leave the numbers alone if it was authored in millimetres.
- Convert the scene. The scene graph is flattened into world space, instances are expanded, and the result is written as one binary STL. Materials and animation are ignored.
- Read the bounds. Check the bounding box before downloading. A metre-scale character should read like a real object in millimetres, not a fingernail-sized trinket.
- Download and slice. Download the STL and import it into your slicer. Check the mesh before a long print; converted game assets often contain open edges.
GLB vs glTF vs STL
| Format | Container | Typical content | Print-ready? |
|---|---|---|---|
| GLB | One binary file | Scene, buffers, images, materials, animation | No — convert first |
| glTF | JSON + sidecar files | Same scene, with external .bin and textures | No — convert first |
| STL | Triangle list | Positions and faces only | Yes, after a mesh check |
The metre trap: why the STL can be 1000× too small
glTF 2.0 defines its unit as metres. STL has no unit field at all, and slicers conventionally read STL numbers as millimetres. A model that is 1.8 units tall in a GLB is 1.8 metres in glTF terms; if you leave the numbers untouched, the slicer sees 1.8 millimetres.
The converter’s Source unit select closes that gap. Pick Metres (m) → mm when the GLB follows the spec, and every coordinate is multiplied by 1000 on the way out. If the file was authored in another unit, pick that source instead. The units and scale guide has the full chain and a calculator for an STL that is already the wrong size.
Draco-compressed GLB
Many GLBs use Draco compression to shrink vertex data. The converter loads a bundled Draco decoder and decompresses the mesh in the tab before writing the STL. Nothing is sent to a decoding service. If the file uses a feature the decoder cannot handle, the page reports the error instead of producing a partial mesh.
Before you slice
- Bounding box. The readout should look like the real object in millimetres.
- Triangle count. Instances expand, so repeated parts can produce more triangles than the GLB size suggests.
- Mesh check. Converted game assets and marketplace downloads often have open edges. Run the slicer’s repair, or inspect it with a mesh report; STL conversion does not make a mesh watertight.
- Licence. A downloaded GLB still carries its author’s licence. Personal printing is usually fine; selling prints may not be.
Questions people ask
Is a GLB the same as a glTF?
They are the same glTF 2.0 scene in two containers. A .gltf is JSON that points to an external .bin and image files. A .glb packs the JSON, binary buffer and images into one binary file, which is why it is easier to move between tools.
Does the converter keep materials and textures?
No. STL stores triangles only: no base colour, roughness, normal map or texture coordinates. The GLB keeps that material work; the STL carries the geometry that a slicer needs.
Can I convert a Draco-compressed GLB?
Yes. The converter uses a bundled Draco decoder, so a compressed GLB is decoded in the tab before the mesh is written. If a file uses a feature the decoder does not support, the page reports the error instead of writing a partial STL.
Why is the STL 1000 times smaller than expected?
glTF coordinates are metres by convention, while STL has no unit field and slicers treat the numbers as millimetres. A 1.8-unit character becomes 1.8 mm unless you choose metres → mm during conversion. The units and scale guide explains the full chain.
Can I convert a GLB that uses a separate .bin?
A GLB does not use a separate .bin; that is the .gltf variant. If you have a .gltf plus its .bin and textures, use the main converter and drop all the files together.
Can I convert several GLB files at once?
Not on this page. It converts one model at a time; the multi-file handling exists for a .gltf and its sidecar .bin, not for batch conversion.
Is the file uploaded?
No. The GLB is read, decoded and written in this browser tab. The conversion makes no upload request; the only copy of the model is the one on your device.
Related: glTF units and STL scale, converting a Sketchfab download, and what each 3D format stores.