Convert STL to 3MF
Drop an STL file below and get a 3MF back. 3MF is the format most modern slicers reach for first: it carries your model's geometry plus real-world units and object grouping in one compact file, instead of the bare triangle soup an STL gives you.
Everything runs inside this browser tab. Your file never leaves your computer, so there's nothing to upload and nothing for us to keep.
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How it works
Good to know
FAQ
Will my model come out the same size?
Yes. The geometry is copied vertex-for-vertex, so dimensions don't change. The practical upgrade is units: STL files have no unit information, so slicers guess (usually millimeters). The 3MF we write declares millimeters explicitly, which removes the 'imported at 1/25th scale' surprise you get when a tool assumes inches.
Does converting add color to my print?
No, and any tool that implies otherwise is overselling. 3MF can store per-object color and materials, but an STL contains none of that, only triangles. We can't invent color that was never in the file. You'll get a clean single-color 3MF; assign colors or materials afterward in your slicer.
Is the 3MF actually smaller than my STL?
Usually, yes. 3MF stores the mesh as compressed XML inside a zip container, so for most models the .3mf is meaningfully smaller than the equivalent ASCII STL and comparable to or smaller than a binary STL. Very small models are the exception, where zip overhead can make them roughly even.
Why use 3MF instead of just keeping the STL?
For printing, 3MF is the more capable container: one file can hold multiple objects with their arrangement, real units, and (when present) color and metadata. Many slicers now default to it. If your model is a single plain part and your workflow is happy with STL, there's no harm in staying on STL, this is an upgrade in tidiness, not a fix for a broken file.
Do you upload my file or store anything?
No. The conversion happens in your browser using your own machine's resources. The file is never sent to a server, we don't see it, and nothing is saved after you close the tab. That's also why large files convert fast: there's no upload wait.