Free OBJ to STL converter

Why convert OBJ to STL?

People convert OBJ to STL because OBJ is decades old, keeps its materials in a second file and knows nothing about animation, while STL is the format every 3D printer and slicer accepts.

How to convert OBJ to STL

1. Choose your OBJ file. Drop it on the box above, or tap to browse. You can pick several files at once.
2. Confirm the target is .stl. It is preselected when your browser can encode it; otherwise the closest available target is chosen. Adjust quality, size or the other options if you want to.
3. Convert and download. Press Convert, then Download. Your file stays on your device the whole time.

What is a .obj file?

OBJ is a plain-text 3D mesh format from the late 1980s that virtually every 3D application can read and write. It stores geometry as vertices and faces, with materials kept alongside in a companion MTL file — simple, ubiquitous, and completely unable to carry animation.

What is a .stl file?

STL describes a surface as nothing but triangles: no colour, no texture, no units. That bluntness is exactly what 3D printing needs, which is why it remains the standard format for sending a model to a printer or a print service.

What to expect from this conversion

Geometry is converted exactly, with node transforms applied so the model keeps its pose. Materials, textures and animation are not carried across. Check the scale in your viewer: STL files carry no units, so a model exported in millimetres can appear a thousand times too large. OBJ keeps its materials in a separate .mtl file, which is not read here — geometry converts, materials do not. STL stores geometry only, so colours, textures and materials are dropped.

Is it private?

Yes, by design. Every conversion happens inside your own browser using your device’s processor — there is no server that receives your OBJ file, so there is nothing for anyone to store, scan or leak. You can confirm it yourself: open your browser’s developer tools, watch the Network tab while you convert, and you will see no upload.

Questions about OBJ to STL

Is this OBJ to STL converter free?

Yes, completely. There is no account, no daily limit, no watermark and no premium tier.

Is my OBJ file uploaded to a server?

No. The conversion runs inside your own browser using your device's processor. The file is read from your disk, converted in memory and saved back to your disk — nothing is transmitted, so there is nothing for anyone to store.

Can I convert OBJ to STL online without downloading software?

Yes. This is an online OBJ to STL converter that runs in your browser, so there is nothing to install and no app to trust with your files. It works the same on a phone.

What happens to the quality?

Geometry is converted exactly, with node transforms applied so the model keeps its pose. Materials, textures and animation are not carried across. Check the scale in your viewer: STL files carry no units, so a model exported in millimetres can appear a thousand times too large. OBJ keeps its materials in a separate .mtl file, which is not read here — geometry converts, materials do not. STL stores geometry only, so colours, textures and materials are dropped.

Can I convert several OBJ files at once?

Yes. Select as many files as you like and they are converted one after another in a single tap, with a download for each and a zip of all of them.

Can I convert OBJ to STL without Blender or a script?

Yes — that is what this page is for. Blender does the same job well if you already have it set up and thousands of files to process; for one file, or a handful, the browser is faster than installing anything.

Should I keep the original OBJ file?

Yes — keep it, converting never touches it. The reason to make a copy in another format is that OBJ is decades old, keeps its materials in a second file and knows nothing about animation.

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