Convert OBJ to STL
Drop an OBJ file below and get an STL back. The conversion runs entirely in your browser — your file is never sent to a server, so nothing leaves your device.
One thing to know up front: OBJ can store colors, materials, and texture coordinates, but STL holds geometry only. This converter keeps the exact shape and drops everything else. For most 3D printing, the shape is all the slicer needs.
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How it works
Good to know
FAQ
Will my colors and textures carry over to the STL?
No. STL is a geometry-only format — there is nowhere in the file to put color, material, or texture data. If your OBJ used an .mtl file or image textures, the STL keeps the shape and silently drops the rest. That's normal and expected; it's a limitation of STL, not a bug. If you need color for printing, look at 3MF or AMF instead.
Does my file actually stay private?
Yes. The conversion happens in JavaScript inside your browser tab. The OBJ is read from your disk into memory, converted, and offered back as a download — it never travels to a server, so we never see it. You can confirm this by disconnecting from the internet after the page loads; the converter still works.
What units and scale will the STL use?
STL files have no unit field — they store raw numbers. We carry your OBJ's coordinate values across unchanged, so the model keeps the same proportions and the same numeric size. If your OBJ was modeled in millimeters, most slicers will read the STL as millimeters too. If it looks 25.4x too big or small, that's usually an inch-vs-mm mismatch you can fix with a scale in your slicer.
Is the STL ready for 3D printing?
Usually, yes — STL is what most slicers and printers expect, and the geometry comes straight from your OBJ. Whether it prints cleanly still depends on the mesh itself: it should be watertight (manifold) with consistent normals. We don't repair holes or non-manifold edges; if your slicer complains, run the original through a mesh-repair tool first, then convert.
Is there a file-size limit?
There's no fixed cap, but because everything runs in your browser, very large meshes are limited by your device's memory rather than by us. Files up to tens of MB convert quickly on a typical laptop. A multi-hundred-MB OBJ may be slow or run out of memory on a phone — desktop handles big files much better.
What's the difference between this and STL to OBJ?
Going OBJ to STL drops color and material because STL can't hold them. Going the other way (STL to OBJ) gives you an OBJ that only contains geometry — it won't magically add colors or materials that were never there. Conversion can drop data that the target can't store, but it can never invent data the source didn't have.