If you've been 3D printing for a while, you've probably noticed that slicers are pushing 3MF over STL. PrusaSlicer defaults to 3MF for project saves. Bambu Studio uses 3MF natively. Even Cura supports it. But is it actually better? Should you switch?
Here's the honest comparison.
Quick comparison
| Feature | STL | 3MF |
|---|---|---|
| Year created | 1987 | 2015 |
| Color data | No | Yes |
| Texture images | No | Yes |
| Multiple objects | No (1 mesh per file) | Yes (full build plate) |
| Multi-material | No | Yes |
| Print settings stored | No | Yes (slicer-specific) |
| Guaranteed watertight | No (common errors) | Yes (by spec) |
| File size (typical) | 5-200 MB | 1-50 MB (compressed) |
| Universal compatibility | Everything supports STL | Most modern slicers |
| CAD software export | All CAD tools | Some (growing) |
| Mesh repair needed | Often | Rarely |
| Open standard | De facto (no formal spec) | Yes (3MF Consortium) |
When to use STL
- Maximum compatibility — every slicer, viewer, CAD tool, and online platform supports STL. If you're sharing files publicly (Thingiverse, Printables), STL is the safest choice.
- Simple single-color prints — if you're printing one object in one material, STL carries everything you need.
- Legacy workflows — older printers, older firmware, or older CAM software may only support STL.
- Quick sharing — STL files are self-contained with no dependencies. Drop one file, it works.
When to use 3MF
- Multi-color prints — Bambu Lab AMS, Prusa MMU, Mosaic Palette. 3MF stores per-region color/material assignments that STL can't.
- Project files — 3MF saves your entire slicer setup: object placement, supports, print settings. Re-open it months later and everything is intact.
- Avoiding mesh errors — STL files frequently have non-manifold edges, inverted normals, and degenerate triangles. 3MF's spec requires a valid mesh.
- Smaller files — 3MF uses ZIP compression. A 100MB STL might be 15MB as 3MF.
The compatibility gap
The biggest downside of 3MF is that not everything supports it yet. Most online 3D model repositories (Thingiverse, MyMiniFactory) primarily deal in STL. Many older CAD tools don't export 3MF. Online viewers that support 3MF are rare — which is partly why we built GeometryViewer's 3MF support.
That said, the gap is closing fast. Every major slicer now reads and writes 3MF. Most new 3D printers ship with 3MF-based workflows. In 2-3 years, the compatibility argument against 3MF will be largely gone.
Our recommendation
Use 3MF for your own workflow. Save PrusaSlicer/Cura projects as 3MF. You get smaller files, preserved settings, and fewer mesh errors.
Export STL for sharing. When uploading to Thingiverse, sending to a client, or sharing publicly, STL is still the most universally compatible format.
Use both in GeometryViewer. GeometryViewer opens STL and 3MF equally well — try it here. You can also preview layer lines and materials on either format.
A note on file size
STL files can get surprisingly large. A detailed miniature might be 80-150MB as STL but only 10-20MB as 3MF, thanks to ZIP compression. This matters when emailing files, uploading to platforms, or storing on SD cards.
If you need to share a 3D model and the STL is too big for email, try converting to 3MF first — or just upload it to GeometryViewer and share the link instead.