Free OFF to STL Converter: No Sign-up, Files Never Uploaded
Turn OFF files into STL for free, with no sign-up and no upload. The conversion happens in this tab, so your files never leave your computer or phone.
The mesh is read as vertices and faces, then written out again as STL.
This pair runs on code that is already in the page, so there is no extra engine to download. STL keeps geometry only; colours, textures and materials are dropped.
- Free
- No sign-up
- Never uploaded
- No watermark
Your files are converted on your device and never uploaded.
How to convert
- Add your OFF files by dragging them onto the converter or by using the file picker.
- Check that STL is the selected target format; it is already chosen on this page.
- Open the options if you want to change scale and units, 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 .off and writes .stl.
- 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.
Supported formats
About the formats
About OFF
Object File Format: a very simple text format for polygon meshes.
Common in geometry research.
About STL
The standard input for 3D printing: geometry only, as triangles.
Has no colour, texture or material data.
OFF vs STL
OFF does not support transparency, and STL does not.
OFF files use the .off extension and STL (3D) files use .stl, so the converted file gets a new name with the new extension.
Privacy: how it works
- Your OFF 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.
- This page converts one way only; STL files cannot be turned back into OFF here.
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 OFF 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 OFF files one at a time if a big batch struggles.
What is the difference between OFF and STL?
OFF does not support transparency, and STL does not. OFF files use the .off extension and STL (3D) files use .stl, so the converted file gets a new name with the new extension.
Can I convert many OFF 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.
Will anything be lost when I convert OFF to STL?
The converter keeps the content of the file. Check the result once, since small differences in metadata or colour handling can happen between formats.
Can I convert STL back to OFF?
Not on this page. This conversion goes one way. Open the STL page to see which formats it can be converted to.