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Vector & CAD format

STL converter

STL is the original 3D-printing file format: a .stl file reduces a solid model to a shell of triangles, each defined by three vertices and a facet normal. Its brutal simplicity — no units, no color, no structure — made it the universal least common denominator for sending shapes to a printer.

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Drop STL files here

Batch files can each use a different output. Nothing uploads for local conversions.

Working inputs include camera RAW, browser-local audio/video, PDF, CBZ/CBR comics, office documents, ebooks, markup, 3D models, structured text, images, and archives.

Where STL comes from

3D Systems created STL in 1987 for the first commercial stereolithography machines built around Chuck Hull's SLA process. The specification has barely changed since, and its longevity owes everything to that stability: nearly forty years on, every slicer and CAD exporter still speaks it.

How STL works

  • Binary STL stores an 80-byte header, a 32-bit triangle count, and fifty bytes per facet; the older ASCII form spells out solid, facet, and vertex keywords.
  • Coordinates are unitless floating-point numbers — receiving software must guess or ask whether a model is in millimeters or inches.
  • No color, material, texture, or multi-object support exists in the core format; competing nonstandard color extensions conflict with each other.
  • Vertices are duplicated per triangle with no shared topology, so files are redundant and non-manifold defects are common.

When to use STL

  • Sending models to slicers for FDM, SLA, and SLS printing
  • Distributing printable designs on model libraries like Printables and Thingiverse
  • Quick mesh export from CAD for clearance and fit checks
  • Capturing 3D scanner output in a universally readable form

Strengths and limitations

Strengths

  • Understood by every slicer, printer, CAD package, and mesh tool without exception
  • Simple to generate and parse
  • The binary form is reasonably compact for what it stores

Limitations

  • Missing units cause real-world scale errors between metric and imperial toolchains
  • Cannot express color, materials, or multi-part assemblies
  • Duplicated vertices bloat files and invite cracks that need mesh repair before printing

Compatibility

Support is as close to universal as 3D formats get: every slicer (PrusaSlicer, Cura, Bambu Studio), every CAD package, and mesh tools from Blender to MeshLab read and write .stl, and Windows and macOS both preview it natively. Its weaknesses are functional rather than compatibility-related — which is exactly why 3MF was designed to replace it.

Essentially none — the binary header offers 80 free-form bytes and the ASCII solid name a single token, neither standardized for metadata.

Convert STL to another format

Convert other formats to STL