Understanding 3D Printing File Formats: STL, 3MF, and AMF

In 3D printing, the file format you choose can significantly impact your workflow, print quality, and ability to collaborate. While STL has been the go-to for decades, newer formats like 3MF and AMF offer advanced features. Let's break down their differences to help you decide which suits your needs.

1. STL (Stereolithography)

Overview: Developed by 3D Systems in the late 1980s for its early stereolithography rapid-prototyping machines, STL is the oldest and still the most universally supported 3D printing format. It represents a model purely as a mesh of triangles approximating its outer surface.

Key Features:

• Geometry only — stores surface data as triangles, nothing else.

• Simplicity — universally compatible with virtually every slicer and printer on the market.

• Large, uncompressed files — no compression, and no curvature data, so smooth surfaces are approximated by potentially thousands of flat facets.

Pros:

• Broadest compatibility of any 3D printing format, across software and hardware alike.

• Simple structure, trivial to generate from any CAD package.

Cons:

• No support for color, texture, material, or multi-body assembly data.

• Larger files and faceted (non-curved) surfaces compared to modern alternatives.

• Carries no embedded unit information — a file can silently be interpreted in the wrong units (mm vs. inch) by the receiving software.

Best for: Hobbyists, quick prototypes, or any situation where maximum compatibility matters more than advanced features.

2. 3MF (3D Manufacturing Format)

Overview: Developed by the 3MF Consortium — founded in 2015 by Microsoft, Autodesk, Dassault Systèmes, HP, and others, with Materialise, 3D Systems, Siemens, and Stratasys joining later — 3MF is a modern, open standard purpose-built to replace STL for additive manufacturing. It became a full ISO standard (ISO/IEC 25) in 2025.

Key Features:

• Rich data — supports color, materials, textures, multi-part assemblies, and manufacturing parameters (bed/hotend temperature, feed rate, per-region materials, support structures) in a single file.

• Compressed XML container — smaller files with more accurate geometry, including true curvature rather than STL's flat-only facets.

• Open standard — freely published and increasingly adopted across the industry.

Pros:

• Compact files carrying far more usable metadata than STL.

• Preserves model integrity — far less detail lost on export compared to STL.

• Growing native support in slicers such as PrusaSlicer, Cura, and Bambu Studio.

Cons:

• Still not as universally supported as STL, particularly on older or budget hardware/software.

Best for: Complex projects needing color, texture, multi-material printing, or embedded print parameters — and for future-proofing a workflow as adoption grows.

3. AMF (Additive Manufacturing File Format)

Overview: AMF is an XML-based format standardized by ASTM/ISO (ISO/ASTM 52915) specifically to address STL's shortcomings for additive manufacturing. It predates 3MF and was, in effect, an early attempt at solving the same problem — 3MF has since taken over as the more actively adopted successor, but AMF remains a recognized open standard in its own right and is still supported by several CAD and slicing tools.

Key Features:

• Curved triangles — unlike STL's flat-only facets, AMF can describe curved surface patches, reducing file size for the same geometric accuracy.

• Color, material, and lattice support — can describe multiple materials, color gradients, and even internal lattice/porous structures within a single file.

• Native units and metadata — unlike STL, units are explicitly defined in the file, removing the mm/inch ambiguity risk.

Pros:

• More geometrically accurate than STL at a comparable file size.

• Genuinely open, vendor-neutral ISO standard.

Cons:

• Support has largely been overtaken by 3MF; fewer actively-maintained slicers prioritize it going forward.

Best for: Workflows already built around ISO-standardized, vendor-neutral formats, or software that adopted AMF before 3MF became dominant.

Comparison at a Glance

Feature	STL	3MF	AMF
Introduced	~1987–88	2015	~2011
Standard body	De facto (3D Systems)	3MF Consortium (ISO/IEC 25, 2025)	ASTM/ISO (ISO/ASTM 52915)
Curved surfaces	No (flat triangles only)	Yes	Yes
Color / texture	No	Yes	Yes
Multi-material	No	Yes	Yes
Print parameters embedded	No	Yes	Limited
Units embedded	No	Yes	Yes
Compression	No	Yes (zipped XML)	Yes (XML, optionally zipped)
Current industry momentum	Still universal, but legacy	Actively growing	Largely superseded by 3MF

A Note on "3AF"

If you've seen "3AF" (sometimes called "3D Advanced Format") described elsewhere as a Dassault Systèmes format for 3D printing, it's worth knowing this doesn't check out against any Dassault documentation, ISO/ASTM standard, or established file-format registry. Dassault does maintain a proprietary lightweight format — 3DXML — but it's designed for visualization, collaboration, and PLM data exchange (viewing assemblies, sharing lightweight 3D data in documents/emails), not for driving a 3D printer or slicer. It isn't a competitor to STL, 3MF, or AMF in an additive-manufacturing context. This is a good example of why it's worth double-checking specifics before publishing — claims like this can slip into circulation from AI-generated sources that sound authoritative but don't trace back to a real spec.

Conclusion: Which Should You Use?

• STL: Stick with it for simple, quick prints, or whenever you're unsure about a printer's or software's compatibility — it's still the safest universal fallback.

• 3MF: Choose this for detailed models needing color, texture, multi-material printing, or embedded print settings — and for future-proofing your workflow, since this is where industry momentum is heading.

• AMF: Relevant mainly if your existing toolchain already standardized on it — new workflows are generally better served by 3MF today.

As 3D printing evolves, 3MF is clearly emerging as the modern successor to STL, with AMF as an important but less actively-developed stepping stone along the way. Understanding what each format actually stores — and doesn't — helps you avoid lost print settings, wrong-scale prints, and compatibility headaches down the line.