Converter · OBJ → STL

Convert OBJ to STL: a file for your slicer in seconds

Your model is an OBJ and your slicer wants an STL. Drop the file: the tool reads the geometry in your browser and writes a compact binary STL, with no account and no upload. The OBJ's materials and textures are not read; an STL cannot hold them anyway.

Nothing is uploaded: everything runs in your browser.

What the conversion keeps and what it drops

STL describes triangles only. The whole shape of your OBJ is kept, including sub-objects, which are merged into one mesh. The .mtl file, textures and UV coordinates are ignored: they have no equivalent in STL. Quads and polygons in the OBJ are split into triangles when the file is read.

Units and scale

Neither OBJ nor STL stores a unit. The numbers are copied as they are: a model exported in meters stays "in meters" in the STL, and most slicers will read it as millimeters, a thousand times too small. Before printing, open the resulting STL in the checker to read its dimensions, then fix the scale in your slicer if needed.

What the conversion does not fix

An OBJ with holes or non-manifold edges gives an STL with holes or non-manifold edges. Conversion is not repair. If your slicer reports errors, the STL checker tells you how many edges are open and whether any edge is shared by more than two faces, so you can fix the mesh in your modeling software.

How it works

  1. Drop the OBJ

    Up to 80 MB on a computer, 40 MB on a phone. Only the .obj is read, not the .mtl.

  2. STL is already selected

    You can pick GLB for the web instead. Losses are shown before converting.

  3. Download the binary STL

    The file is written on your device. Check its dimensions before slicing.

Frequently asked questions

My OBJ has textures. Will they be in the STL?
No. The STL format stores shape only. Colors, textures and the .mtl file are lost, and the tool says so before converting. To keep colors for the web, convert to GLB instead.
Is the STL binary or ASCII?
Binary: more compact and read by every slicer. An ASCII STL would be three to four times larger.
Why does my model come out tiny or huge in the slicer?
The OBJ has no stored unit. If it was modeled in meters or inches, the slicer reads it as millimeters. The STL checker shows the size in the unit of your choice so you can spot the issue, then you rescale in the slicer.
Is my file uploaded to a server?
No. Reading and writing both happen in your browser. Nothing is uploaded or kept, and no account is needed.

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