Convert GLB to STL for 3D printing
Drop the GLB on Polymend. It turns the model upright, lets you set its print height in millimeters, repairs the small mesh faults a slicer would flag, and gives you an STL, a 3MF or both. It is free, it runs in your browser, and the file is never uploaded. Color and texture are not kept, since an STL holds shape only.
Why a GLB needs converting
A GLB is a binary glTF file, made for showing 3D models on screens. Slicers prefer STL or 3MF, and a GLB that is renamed or exported carelessly tends to arrive wrong in three ways:
- Size. glTF measures in meters, while an STL has no units and slicers read it as millimeters. A 20 cm figure can arrive 0.2 mm tall.
- Direction. glTF treats Y as up; printers treat Z as up. Unturned, a standing figure lies on its back.
- Mesh faults. Models made for screens often carry small holes, stray triangles and reversed faces. A screen does not mind them; a slicer reports them as open edges, non-manifold edges and reversed faces.
How to convert it with Polymend
- Open polymend.xyz and drop in one GLB, or up to 20 at once.
- Check the model before and after, side by side. Every change is marked, and you can step through them one at a time.
- Under Size, set the print height in millimeters.
- Download an STL, a 3MF, or a ZIP with both.
A detailed figure of 300,000 triangles takes about a second. Files up to 200 MB or 1 million triangles work on a laptop.
GLB files that need a little more
- Draco-compressed GLB files, which many museums and model sites publish, are unpacked automatically.
- Meshopt-compressed GLB files are not supported yet. Export them again uncompressed.
- Rigged or animated GLB files are read in their rest pose. If the file has animation clips, you can choose any moment of a clip and repair that pose instead.
Questions
Can I convert GLB to STL without uploading the file?
Yes. Polymend reads and converts the file in your browser. The page carries a security policy that tells your browser to block it from opening any network connection, and the code is open source, so this can be checked.
Should I use STL or 3MF?
Either works in most slicers. A 3MF records its units, so it always opens at the size you set. An STL has no units, and slicers assume millimeters, which is what Polymend writes.
Why is my converted model tiny in the slicer?
The GLB was measured in meters and the slicer read the numbers as millimeters, so a model 0.2 m tall became 0.2 mm. Setting a print height in Polymend before you download writes the model at that size.
Can I convert GLB to STL in Blender instead?
Yes: import the glTF file, then export it as STL, setting the scale and turning it upright yourself. Blender does not repair the mesh on export, so a slicer may still report open or non-manifold edges.
