GLOSSARY
3MF File
3MF is a modern 3D printing format that bundles geometry, materials, colors, units, and slicer settings into a single zipped file. Increasingly the default in Bambu Studio and PrusaSlicer.
Definition
3MF was developed by the 3MF Consortium (Microsoft, HP, Autodesk, Bambu, Prusa, and others) as a replacement for STL. Internally it is a ZIP archive containing XML descriptions of the mesh, plus optional textures, color information, multi-part assemblies, units, and slicer-specific settings.
Because it carries metadata, a single 3MF file can represent a printable plate of multiple parts with different materials, AMS color assignments, supports already authored, and the exact slicer profile used. Sharing a 3MF instead of an STL is now the convention in the Bambu and Prusa communities.
Why it matters
3MF eliminates two recurring STL problems: missing units (3MF stores them) and lost slicer settings (3MF embeds them). When someone hands you a 3MF from Printables or MakerWorld, you open it and the print plate is already laid out, supports placed, profile selected.
For multi-color and multi-material printers (Bambu AMS, Prusa MMU, XL toolchangers), 3MF is essentially required — STL cannot describe which body uses which filament.
Common confusion
3MF files come in two flavors in practice. A "model 3MF" contains just the mesh and is interoperable across slicers. A "project 3MF" (Bambu Studio, OrcaSlicer, PrusaSlicer) contains slicer-specific data and may not open cleanly elsewhere.
AMF, an older XML-based format, attempted to solve the same problems and never caught on. 3MF is the one that won.