FORMAT COMPARISON
STL vs 3MF
The old universal and the modern replacement — what each stores, when to use which, and why you still need both.
The short answer
Use 3MF when your slicer saves and reads it — Bambu Studio, PrusaSlicer, OrcaSlicer, and Cura all do. Use STL when you need maximum compatibility: every tool since 1987 reads it. In practice you will use both. 3MF is the slicer project; STL is the interchange format when you are sharing or converting and cannot assume what the other end speaks.
Feature comparison
The gap is not “old vs new” so much as “triangles vs a package.” STL won by being the smallest thing every program could write. 3MF exists because that smallest thing forgot units, color, and which object is which.
| Feature | STL | 3MF |
|---|---|---|
| File structure | Raw triangle list | ZIP archive (XML + optional textures) |
| Geometry | Triangles only | Triangles, with indexed vertices |
| Units | None — slicers assume mm | Declared in the file (mm) |
| Color / materials | No | Yes (per-triangle, per-vertex, textures) |
| Multiple objects | One solid per file | Multiple objects in one file |
| Print settings (infill, supports) | No | Yes — slicer projects live here |
| Metadata (author, title) | No | Yes |
| Typical file size | 50 bytes × triangles + 84 | Compressed — often smaller |
| First released | 1987 | 2015 |
| Spec owner | 3D Systems (de facto public) | 3MF Consortium (Microsoft, HP, etc.) |
When to use STL
- Sharing with someone whose tools you don't control
- Uploading to a print service that only accepts STL
- A quick geometry check in a viewer
- Converting from another format — everything exports STL
When to use 3MF
- Saving a slicer project with settings intact
- Multi-color / multi-material prints (Bambu AMS)
- Sharing a complete print-ready package
- When you want units declared in the file
Converting between them
STL → 3MF wraps geometry in a 3MF container. 3MF → STLextracts geometry and drops settings and color. Neither direction creates data that wasn't there. A color 3MF does not become a color STL; an STL wrapped as 3MF does not gain infill or supports.
FAQ
Is 3MF replacing STL?+
Slowly. Modern slicers default to 3MF for project files, but STL is still the universal exchange. Think of 3MF as the better project format and STL as the lowest common denominator. You will keep both for the foreseeable future.
Can I use both?+
Yes — that is what most workflows look like. Export STL from CAD, import into the slicer, save as a 3MF project. Or receive a 3MF from someone, convert to STL if your tool needs it. Neither format has to win.
Which is smaller?+
3MF, usually. It uses ZIP compression and indexed vertices. Binary STL repeats every vertex (50 bytes per triangle). A 1M-triangle model is ~48 MB as STL; the same mesh in 3MF is often under 15 MB.
Does converting STL to 3MF add color?+
No. Converting wraps the same triangles in a 3MF container. Color and materials only appear if the source had them — STL never does. Open the result in a slicer and assign colors there.
Which format do print services accept?+
Most accept STL. Some (Shapeways, i.materialise) also accept 3MF. If you are uploading to a service, check their format list — STL is the safe bet.