3D printing · Meshes · CAD drawings
STL is a flat list of triangles with every corner written out separately, and no units. 3MF is a zipped XML container with an indexed vertex pool, real units, and room for materials and colour. Same geometry, considerably better container.
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stl · 3mf · obj · ply · amf · dxf · svg · gcode
STEP export merges coplanar triangles into real planar faces, so flat surfaces come through as single selectable, dimensionable planes and CAD imports them quickly. Curved surfaces stay faceted, and there are no parametric features — a mesh has no record of them. Simplify is optional here; leave it off for the most accurate dimensions.
Working
In an STL, a vertex shared by six triangles is stored six times. 3MF stores it once and refers to it by index, so the same model is typically a third of the size before compression even starts.
STL records no unit at all, which is the most common reason a model arrives 25.4 times too large or too small. 3MF states its units, so the ambiguity disappears.
The conversion is exact. Every triangle survives; the only change is that duplicate vertices are welded into a shared pool, which is what the format expects.
See all supported formats — meshes, 2D drawings and g-code, all converted in your browser.
For 3D printing, generally yes. 3MF stores units, materials and colour, and uses an indexed vertex pool that makes files considerably smaller. STL stores triangles only, with no units at all.
No. Every triangle is preserved exactly. Duplicate vertices are welded into a shared pool, which is what the format expects and does not change the geometry.
PrusaSlicer, Bambu Studio, Cura, Orca and most current slicers read 3MF natively. Some older software still expects STL.
If a file will not convert, or the result looks wrong, I would rather hear about it. Include the format and roughly what you were doing — that is usually enough to reproduce it.