3MF vs STL: differences and which one to use
STL has been the 3D printing standard for 30 years, but for multicolor parts 3MF is clearly better. Here's why.
What an STL is
STL describes an object's surface as a list of triangles. That's it: no colors, materials, units or relative placement of multiple parts. It's universal —every program opens it— but very limited. For a two-color part you need two STL files and must align them by hand.
What a 3MF is
3MF (3D Manufacturing Format) is an open standard created by an industry consortium (Microsoft, HP, Autodesk, Prusa, Ultimaker, among others). It's a .zip with XML inside that stores the mesh plus colors, materials, units (always millimeters) and multiple parts in one file, already positioned.
Comparison
| Feature | STL | 3MF |
|---|---|---|
| Colors and materials | No | Yes |
| Multiple parts in one file | No | Yes |
| Units | Ambiguous | Millimeters |
| File size | Large | Small (compressed) |
| Print settings | No | Optional |
| Compatibility | Universal | All modern slicers |
Which slicers open 3MF
- Bambu Studio and OrcaSlicer: yes, with per-part filament assignment.
- PrusaSlicer: yes; loads the parts as one object with multiple parts.
- UltiMaker Cura: yes (since version 4).
- Creality Print and Anycubic Slicer Next: yes.
- Very old programs and some resin printers: STL only.
When to use each
Use 3MF whenever your slicer supports it, especially for two-color parts like a QR code: open the file and the base and relief already appear separated with their colors. Use STL only if your program can't open 3MF; QRelieve gives you a .zip with both parts and a README.
💡 When importing two STLs, load them together and, if asked, choose “single object with multiple parts” so they stay aligned.
How to open a 3MF step by step
- Download the 3MF from the tool and save it somewhere easy to find.
- Open your slicer and use File → Import (or drag the file into the window).
- If you get a “file not created with this program” or “load geometry only” notice, accept it: the parts' colors are kept as separate parts.
- Check the object list shows two parts and assign a filament to each.
- Don't scale the parts separately: if you resize, scale the whole object.
Common import problems
- Parts appear apart on the bed: the slicer loaded them as two objects. Select both and group them, or re-import choosing “one object with multiple parts”.
- The relief floats or sinks: never move one part without the other; undo and move the assembly.
- Colors aren't assigned automatically: some slicers ignore stored colors; assign them by hand, it's only two parts.
- The file is large: QR codes in the “Dots” style have more geometry. That's normal; slicers handle it fine.
Frequently asked questions
Can I convert a 3MF to STL? Yes, any slicer can export each part as STL, but you lose the colors. Does 3MF store print settings? It can, but QRelieve files only include geometry and colors so you can use your own profile. Does it work for resin printers? For resin, use the base STL, since they print a single material.