Free STL Converter: No Sign-up, Files Never Uploaded
Convert STL files free, right in your browser. There is no sign-up or login, no watermark, and nothing is uploaded: your 3D models never leave your device.
STL (3D) in short. The standard input for 3D printing: geometry only, as triangles. Has no colour, texture or material data.
From STL you can convert to OBJ, GLB, glTF, PLY, USDZ and PNG. These pairs run on code already in the page, with no extra engine to download.
- Free
- No sign-up
- Never uploaded
- No watermark
Your files are converted on your device and never uploaded.
How to convert
- Add your STL files by dragging them onto the converter or by using the file picker.
- Choose the format you want from the list of targets that fit your file.
- Open the options if you want to change quality or size, or keep the defaults.
- Press Convert and watch the progress shown for each file.
- Download each result, or take them all together as one ZIP when you converted several files.
Features
- Reads .stl files and can also write them.
- Free, with no watermark added to the result.
- No sign-up and no login.
- Your files are never uploaded and never leave your device.
- Batch conversion with a ZIP download for several results.
- The input is recognised by its content, not only by its file name.
- 6 target formats to choose from.
Supported formats
| Format | Read | Write | Notes |
|---|---|---|---|
| Wavefront OBJ.obj | Yes | Yes | Plain-text 3D mesh format from Wavefront, supported by almost every 3D tool. |
| STL (3D).stl | Yes | Yes | The standard input for 3D printing: geometry only, as triangles. |
| GLB.glb | Yes | Yes | Binary glTF: a whole 3D scene in a single file. |
| glTF.gltf | Yes | Yes | JSON-based glTF, usually with separate files for geometry and textures. |
| PLY.ply | Yes | Yes | Polygon File Format, developed at Stanford for 3D scanner data. |
| 3MF.3mf | Yes | No | Writing 3MF is not offered; read it and export OBJ, STL or GLB instead. |
| FBX.fbx | Yes | No | FBX is Autodesk’s proprietary format, so it can be read but not created. |
| Collada (DAE).dae | Yes | No | Collada is read only here; export to GLB or glTF instead. |
| OFF.off | Yes | No | OFF is a simple research format that is read only here; convert it to OBJ or STL. |
| 3DS.3ds | Yes | No | 3DS is a legacy format that is read only here; convert it to OBJ or GLB. |
| USDZ.usdz | No | Yes | Apple’s packaged 3D format for AR Quick Look on iPhone and iPad. |
About the formats
About STL
The standard input for 3D printing: geometry only, as triangles.
Has no colour, texture or material data.
It does not support transparency.
What STL can become
STL to OBJ runs in the page.
STL to GLB runs in the page.
STL to glTF runs in the page.
STL to PLY runs in the page.
STL to USDZ runs in the page.
STL to PNG runs in the page. A still preview rendered from a default camera angle.
Converting to STL
Pages for converting to STL start from OBJ, GLB, glTF, PLY, 3MF, FBX and OFF.
Privacy: how it works
- Your STL files stay on your device. The page reads each file with the browser's file API, converts it with code running in the tab, and hands the result back as a download. No upload happens, so there is no copy of your file on our servers to protect, delete or leak.
- There is nothing to sign up for and no login. The converter does not ask for an email address, and it does not need to know who you are to do its job.
- You can check the claim yourself: open your browser developer tools, watch the Network tab while a file converts, and you will see no request that carries your file.
Tips
- Check the scale and the units in your slicer or viewer after conversion.
- Colours and textures only survive between formats that can store them; STL keeps geometry only.
- Keep the original model as the master.
- Preview the converted file before you print or publish it.
Frequently asked questions
Is it really free?
Yes. There is no price, no trial, no credit card and no watermark added to your results. Ulkaa Tool does the conversion with your own device, so there is no server bill to pass on to you.
Are my files uploaded?
No. Your STL files are read and converted inside your browser and are never sent to Ulkaa or to anyone else. The result is created on your device and you save it from there.
Do I need an account?
No. There is no sign-up and no login. Open the page, add your files and convert. An Ulkaa account is not needed for anything on this tool.
Is there a file size limit?
No limit is set by us. The real limit is your device: the conversion uses your own memory and processor, so very large files can be slow or fail on a weak phone or an older computer. Close other heavy tabs and convert STL files one at a time if a big batch struggles.
What can I convert STL files to?
You can convert STL to OBJ, GLB, glTF, PLY, USDZ and PNG. Pick one on the converter and it applies to every file you add.
Can I convert other files to STL?
Yes. OBJ, GLB, glTF, PLY, 3MF, FBX and OFF can be converted to STL.
Can I convert many STL files at once?
Yes. Add as many files as your device can handle. Each one is converted on its own and you can download them one by one or as a single ZIP.