STL is a useful way to share a model’s surface geometry. A 3MF file can carry more: multiple objects, units, colors and application-specific information. But a file ending in .3mf is not necessarily a complete, portable set of print settings.
The important distinction is between a model exported as 3MF and a slicer project saved as 3MF. Decide which one you need before choosing the download or export command.
What survives the handoff?
| File or operation | What the recipient can expect | What still needs checking |
|---|---|---|
| STL model | Surface triangles describing geometry | Intended dimensions, material, orientation and slicing settings |
| 3MF model export | Geometry plus the information that exporter actually writes | Supported properties and extensions in the receiving application |
| PrusaSlicer Save Project As | Objects, settings, modifiers and their parameters | Slicer compatibility and suitability for the recipient’s printer |
| Import a model into an existing project | Model input through that application’s import operation | Whether the operation deliberately leaves current settings in place |
The first two rows describe file capabilities, not a promise about every program. The 3MF Consortium FAQ explains the limitations of STL and the richer manufacturing information 3MF was designed to carry. Prusa documents the specific contents of its saved project files .
Why the same 3MF can behave differently
PrusaSlicer’s documented commands distinguish opening a project with configuration from importing a model without configuration. That difference can explain why a downloaded file brings in a shape but does not reproduce the sender’s setup. Check the operation you selected before assuming the file is broken. See Prusa’s command reference .
Conversely, accepting a project’s settings is not proof that they suit your machine. Review the printer profile, nozzle, filament and object arrangement before slicing. A file prepared for a different printer is still a different setup, even if the model looks right on the screen.
Keep dimensions explicit
The versioned 3MF Core specification defines a model unit field, with millimeters as its default. This helps communicate scale, but it does not replace a dimension check after import.
For example, if the designer says a bracket is 80 mm wide, compare that intended width with the imported object’s displayed width. Record the known dimension alongside the file. A recognizable silhouette alone cannot tell you whether a unit conversion went wrong.
For a simple geometry handoff, send the model and its intended dimensions. For someone continuing a PrusaSlicer setup, send the saved project and identify the slicer version and target printer. Keep the original CAD file separately when future design edits matter; a manufacturing mesh is not a substitute for the editable design history.
How this comparison was made
This is a documentation comparison of file capabilities and named PrusaSlicer operations, checked October 12, 2026. We did not test cross-slicer imports or print the same model in different formats. File size, speed and finished-part quality are not ranked here.