Convert OBJ to STL
Free · no signup · no watermark · runs in your browser · batch up to 20 files, download as ZIP
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This free OBJ to STL converter turns your .obj models into .stl files. OBJ is the old universal interchange format that every 3D program reads, usually with an .mtl material file and texture images beside it.
This conversion runs entirely in your browser. The file is never uploaded, which makes it instant, private and usable on work files you would not want to send to a stranger's server.
It also works as a bulk OBJ to STL converter: drop up to 20 OBJ files at once, they are converted one after another in your browser, and you can download each file on its own or all of them together in a single ZIP. A file that fails is listed with the reason and does not stop the rest of the batch.
How to convert OBJ to STL
- Drop your OBJ files onto the box above, or click it to choose from your computer. Up to 20 at once.
- Check the 3D preview and model info. If the model is the wrong size or lying on its back, open the options to set the source units or rotate Z-up to Y-up, then press Convert.
- Download each converted file from the list, or press "Download all (.zip)" to get the whole batch in one ZIP file.
What changes when you convert OBJ to STL
STL stores triangles only, so any colours, materials, textures, UVs and animation in the OBJ file are dropped. The geometry itself is kept exactly.
OBJ and STL compared
| OBJ | STL | |
|---|---|---|
| Full name | Wavefront OBJ | Stereolithography |
| Extension | .obj | .stl |
| MIME type | model/obj | model/stl |
OBJ: Plain-text geometry with UVs and normals, read by nearly every 3D program. Materials live in a separate .mtl file and textures beside it; there is no animation and no unit.
STL: The 3D printing workhorse: a list of triangles and nothing else. No colour, no materials, no UVs and no units (millimetres by convention), which is why every slicer and CAD tool can read it.
Frequently asked questions
How do I convert OBJ to STL?
Drop your .obj file onto the box on this page and the .stl file is ready to download in a second or two. There is no signup, no email, no watermark and no file limit beyond what your browser can hold in memory.
Is this OBJ to STL converter free?
Yes, completely, with no account, no trial and no watermark on the output. There is nothing to buy on this page: choose a file, convert it and download the result.
Are my files uploaded anywhere?
No. This conversion runs entirely in your browser using JavaScript, so the file never leaves your computer. You can disconnect from the network after the page loads and it will still work.
Will converting to STL reduce the quality?
STL stores triangles only, so any colours, materials, textures, UVs and animation in the OBJ file are dropped. The geometry itself is kept exactly.
Can I convert multiple OBJ files to STL at once?
Yes, up to 20 files in one go. Drop or select them all together and they are converted one after another. Each file appears in the results list with its own download button, and "Download all (.zip)" saves the whole batch as a single ZIP. If one file cannot be converted, it is listed with the reason and the others still finish. For more than 20, run a second batch.
Found a problem, or something that could be better? We read every message and we fix things quickly.
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