# STL to GLB Converter

> Put a printable part on a website, in AR or in a three.js scene: STL to GLB at its real size, standing upright, in a file about a third the size of the STL.

Page: https://printpal.io/convert/stl-to-glb
Updated: 2026-11-12
Use it: open https://printpal.io/convert/stl-to-glb in a browser and drop a file. Free, no account, files are processed locally and never uploaded.

GLB is the web's 3D format and the only common one whose units and axes are fixed: metres, Y up. The converter turns the STL's millimetres into metres and its Z up into Y up, so a 50 mm part shows at 5 cm and upright in any glTF viewer, Android's Scene Viewer or a three.js page.

STL repeats every corner for every triangle. The GLB shares them and leaves normals to the viewer (glTF readers shade such meshes flat, like the STL), which typically makes the file about a third of the STL's size. It gets a neutral grey material you can restyle in any editor.

## How to convert STL to GLB

1. **Drop your STL files.** Drop one or more .stl files, binary or ASCII, or a .zip of them.
2. **Check the preview.** The model appears at the size and orientation it will have. Fix the file units, up axis or size under Size, units and orientation if needed.
3. **Choose GLB options.** No options needed: GLB is written in metres, Y up, with materials and textures embedded.
4. **Convert and download.** One file downloads straight away. A batch gives a download per file and one .zip of all of them.

## What carries over

| | Result |
|---|---|
| Geometry | Every triangle is kept at full precision. |
| Color | STL has no color to carry. The GLB comes out uncolored. |
| Units | Converted from millimetres to metres, so it keeps its real size. A 50 mm part is written as 0.05. |
| Orientation | Turned from Z up to Y up, so it stands upright in web viewers and AR. |
| Objects | Each part stays a separate object or mesh. |

## STL at a glance (Stereolithography (Standard Triangle Language))

Created by 3D Systems in 1987 for the first stereolithography printers, STL is still the format every slicer and print service accepts. It describes a surface as a list of independent triangles, with no shared vertices, units, colors or scene structure.

- **Stores:** Loose triangles: three corners and a normal each, binary or ASCII
- **Color:** None in the standard
- **Units:** None written; slicers assume millimetres
- **Up axis:** Z, the slicer convention
- **File size:** 50 bytes per triangle in binary, about 5 times that as ASCII
- **Opens in:** Every slicer, CAD tool and 3D app

## GLB at a glance (glTF 2.0 binary)

glTF 2.0 is the Khronos Group's "JPEG of 3D", and GLB is its single-file binary form. It is what AI 3D generators, Sketchfab downloads and web apps hand out, and it is the only common format whose units (metres) and axes (Y up) are fixed by the spec.

- **Stores:** Meshes, PBR materials, textures, animation and scenes in one binary file
- **Color:** Full: textures, base colors and vertex colors
- **Units:** Metres, fixed by the glTF spec
- **Up axis:** Y, fixed by the spec
- **File size:** Compact; Draco or Meshopt compression shrinks meshes 5 to 10 times
- **Opens in:** Web viewers, Blender, Windows, Android Scene Viewer, Godot, Unity and Unreal importers

## Tips

- **For iPhone AR** Apple's AR Quick Look wants USDZ: use [STL to USDZ](https://printpal.io/convert/stl-to-usdz).
- **Make it lighter** For big scans, compress the GLB with Draco or Meshopt (for example with glTF-Transform) for another 5 to 10 times.
- **Product pages** Put the GLB in a `<model-viewer>` tag to show a print in 3D on your shop.

## FAQ

### Why is my GLB tiny in Blender?

It isn't: glTF is in metres, so a 50 mm part is 0.05 m, its real size. Blender shows it at that size.

### Does the GLB keep flat facets?

Yes. It has no normals, so viewers shade each triangle flat, the same look as the STL.

### Can I convert many STLs to GLB at once?

Yes. Drop them all or a .zip and download every GLB in one .zip.

### Is the converter free? Are there limits?

Free, with no sign-up, watermark or file count limit. Batches and files of a few hundred MB work on most laptops; the only limit is your device's memory.

### Are my files uploaded?

No. Files are read and written by JavaScript and WebAssembly in your browser and never sent to PrintPal. The STEP and IGES reader is the only extra download, once, from a public CDN.

## Related

- [STL to OBJ Converter](https://printpal.io/convert/stl-to-obj)
- [STL to 3MF Converter](https://printpal.io/convert/stl-to-3mf)
- [GLB to STL Converter](https://printpal.io/convert/glb-to-stl)
- [GLB to OBJ Converter](https://printpal.io/convert/glb-to-obj)
- [GLB to glTF Converter](https://printpal.io/convert/glb-to-gltf)
- [STL to PLY Converter](https://printpal.io/convert/stl-to-ply)
- [GLB to 3MF Converter](https://printpal.io/convert/glb-to-3mf)
- [GLB to USDZ Converter](https://printpal.io/convert/glb-to-usdz)
- [3D model viewer](https://printpal.io/tools/3d-model-viewer)
- [3D model converter](https://printpal.io/tools/3d-model-converter)
- [Mesh Repair](https://printpal.io/tools/mesh-repair)
- PrintPal for LLMs: https://printpal.io/llms.txt