What is STL?

STL (Stereolithography or Standard Triangle Language) represents 3D objects using triangular facets. Each triangle is defined by three vertices and a normal vector. By combining thousands or millions of tiny triangles, STL files can approximate any 3D shape. The format stores only geometry - no color, texture, or material information.

STL is the de facto standard for 3D printing - supported by every 3D printer, slicer software (Cura, PrusaSlicer), and CAD program. Files come in ASCII (human-readable text) or binary (compact) formats. While simple and universal, STL has limitations for complex models, leading to newer formats like 3MF, but remains dominant due to widespread compatibility.

Did you know? STL files power billions of 3D printed objects worldwide!

History

STL was created by 3D Systems for their stereolithography 3D printers and became the universal standard as 3D printing technology spread.

Key Milestones

  • 1987: STL format created by 3D Systems
  • 1990s: Adopted by CAD software
  • 2009: RepRap makes 3D printing accessible
  • 2012: Consumer 3D printer boom
  • 2015: 3MF format introduced (but STL remains)
  • Present: Universal 3D printing standard

Key Features

Core Capabilities

  • Universal Compatibility: Every 3D printer
  • Simple Format: Easy to generate/parse
  • Triangle Mesh: Approximates any shape
  • Binary/ASCII: Two format options
  • Geometry Only: Pure shape data
  • Industry Standard: De facto format

Common Use Cases

3D Printing

FDM, SLA, SLS printers

Prototyping

Rapid product development

Medical

Surgical models, prosthetics

Hobby/Maker

DIY projects, models

Advantages

  • Universal 3D printer support
  • Simple and well-documented
  • Wide software compatibility
  • Easy to generate from CAD
  • Both ASCII and binary options
  • Industry standard for decades
  • Open format

Disadvantages

  • No color or texture support
  • Large file sizes for complex models
  • Only surface geometry (no volume)
  • No units specification
  • Can have mesh errors
  • No metadata or materials

Technical Information

Format Specifications

Specification Details
File Extension .stl
MIME Type model/stl, model/x.stl-binary
Format Type 3D mesh
Variants ASCII, Binary
Structure Triangular facets
Typical Size 100 KB - 100 MB

Common Tools

  • CAD: Fusion 360, SolidWorks, Blender, Tinkercad
  • Slicers: Cura, PrusaSlicer, Simplify3D
  • Viewers: MeshLab, 3D Builder, Windows 3D Viewer
  • Repair: Netfabb, Meshmixer