STL to GLB

STL to GLB: put a printable model on the web

This page converts STL to GLB in your browser. Drop an STL, check it in the preview, and download a GLB that web viewers, AR apps and game engines can load. The file is never uploaded.

STL is the right format for a slicer, but almost nothing on the web displays it natively. GLB, the binary form of glTF, is what web 3D viewers, the model-viewer element and Android's Scene Viewer expect. If you sell printed parts or share designs and want people to spin the model around on a product page, or place it on their desk in AR before ordering, converting STL to GLB is the usual first step.

How to convert STL to GLB

1. Drop the .stl file onto the converter, or click to choose it. ASCII and binary STL both work.

2. Check the model in the preview.

3. Keep “Fix up axis” on unless you know the STL is Y-up.

4. Click Convert. The .glb downloads straight away, and its size is shown so you can judge whether it is light enough for a web page.

For a product page, a very dense STL (millions of triangles from a high-resolution export) makes a heavy GLB that loads slowly on phones. Exporting the STL at a coarser resolution, or decimating the mesh in a 3D editor, keeps the page fast.

To turn a GLB from a game or scan into something you can print, use GLB to STL.

What you get in the GLB

A GLB can store far more than an STL holds, so the conversion is about what the STL brings, and what it doesn't:

Geometry

Kept, triangle for triangle. The converter does not simplify or repair the mesh.

Shading

The STL's facet normals come across, so curved surfaces look as faceted in the GLB as they did in the slicer. A finer STL export gives smoother curves.

Material

A plain default PBR material. STL has no materials to bring along. To make it look like a specific filament or resin, set the material color and roughness in a 3D editor afterwards.

Color

Almost no STL files carry color. The rare binary STL with per-face colors shows them in the preview, but don't count on them as a finish for a product page.

Size

The numbers are copied unchanged; see the note on units below.

File size

Binary STL packs each triangle into 50 bytes. GLB stores a position and a normal for every corner, so the GLB is often somewhat larger. The output size is shown after converting.

Millimeters in, meters out

This is the one thing that catches people. STL files for 3D printing are almost always in millimeters, though the file itself never says so. glTF is defined in meters. The converter doesn't rescale, so a 60 mm figurine becomes a GLB that is 60 units tall, and glTF software reads that as 60 meters.

In a normal web viewer you won't notice: the camera frames whatever it is given. In AR you will, because AR viewers place models at real-world size, and your figurine will tower over the room. Most AR viewers let the visitor pinch to resize, but if you want the model to appear at its true size, open the GLB in a 3D editor such as Blender, scale it by 0.001 and export it again.

Standing upright: the up-axis fix

Slicers and CAD programs are Z-up. glTF is Y-up. Taken across without a correction, a part that stood on the print bed would be lying on its back in every web viewer. “Fix up axis” is switched on by default here and rotates the model 90 degrees so it stands the way it stood on the bed.

Turn it off only if the STL came from a Y-up program, which is uncommon for files made for printing. The preview shows the input as an STL viewer would; if the downloaded GLB comes out lying down, convert again with the checkbox flipped.