STL vs OBJ vs GLB vs 3MF vs STEP — Every 3D File Format Explained

Quick Comparison

STL — The Universal Standard

STL (Standard Tessellation Language, or StereoLithography) is the oldest and most widely supported 3D printing format. It represents geometry as a mesh of triangles — no color, no material, no parametric data. Just the shape.

• Supported by every slicer: Cura, PrusaSlicer, Bambu Studio, Chitubox, Lychee
• Two variants: ASCII (human-readable, larger) and Binary (compact, default)
• No native support for colors, textures, or multiple materials
• Can represent non-manifold (broken) geometry — always check with a mesh repair tool

When to use STL: Upload STL when your model is print-ready and your buyers are using FDM or resin printers. It's the safest choice for maximum compatibility. On Proofly, every STL download gets a unique HiddenMark™ watermark embedded in the mesh geometry.

OBJ — Colors and Multi-Material Meshes

OBJ (Wavefront Object) is a text-based format that supports vertex colors and material references via a companion .mtl file. It's a staple in 3D rendering pipelines and older workflows.

• Supports vertex colors and UV-mapped textures via .mtl sidecar files
• Widely supported in Blender, Maya, 3ds Max, ZBrush
• Partial slicer support — some slicers ignore materials
• Files are large (ASCII text); a 50 MB OBJ can exceed 200 MB uncompressed vertices

When to use OBJ: Good for multi-color or textured models targeted at rendering artists or game developers. When selling, bundle OBJ + MTL + textures in a ZIP package so buyers get everything they need.

GLB — The Web 3D Standard

GLB is the binary container for the glTF 2.0 format — the "JPEG of 3D" according to Khronos Group. It packages geometry, textures, materials, and animations into a single compact file.

• Supports PBR (Physically Based Rendering) materials with full texture maps
• Animations and skeletal rigs supported natively
• Renders in every modern browser — no plugin needed
• The format used by Proofly's in-browser 3D viewer for instant previews
• Smaller than OBJ thanks to binary encoding and texture compression (KTX2/Basis)

When to use GLB: Upload GLB if you want buyers to preview your model in the browser before downloading. Ideal for game-ready assets, figures with painted details, or props with PBR materials. Not intended for slicing (use STL for print-ready output).

3MF — The Modern Printing Standard

3MF (3D Manufacturing Format) was designed specifically to replace STL for 3D printing. It's an open standard backed by Microsoft, HP, Autodesk, Ultimaker, Stratasys, and others.

• Stores color, material, and multi-extruder information natively
• Guarantees watertight (manifold) geometry by spec — no broken meshes
• Includes slicer metadata: scale, orientation, support settings, print profiles
• Smaller file size than equivalent STL (binary + optional compression)
• Supported by PrusaSlicer, Bambu Studio, Cura, Chitubox, Microsoft 3D Builder

When to use 3MF: Offer 3MF alongside STL for a premium experience — buyers get color data, better print orientation defaults, and guaranteed clean geometry. Multi-color models (for multi-material printers like Bambu X1C) should always ship as 3MF.

STEP — Parametric CAD Files

STEP (Standard for the Exchange of Product Model Data, ISO 10303) is the lingua franca of professional CAD and engineering. Unlike mesh-based formats, STEP stores exact curves, surfaces, and dimensional constraints — the full parametric history of a part.

• Exports from every professional CAD tool: Fusion 360, SolidWorks, FreeCAD, Onshape, CATIA
• Retains exact geometry (no triangle approximation) — ideal for CNC machining
• Not intended for slicers — always convert to STL/3MF before printing
• Standard in industrial and engineering procurement
• Proofly accepts .step/.stp files — perfect for engineering, functional parts, and precision mechanical models

When to use STEP: Sell STEP files when your buyers are engineers, machinists, or designers who need to modify your part. Bundle STEP + STL in a ZIP package: the STL for printing, the STEP for editing. This dramatically increases the perceived value of your listing.

Which Format Should You Upload to Proofly?

Frequently Asked Questions