The Short Answer
An STL file is a 3D model. It's the digital blueprint for a physical object. You load it into slicer software, which converts it into instructions for your 3D printer, and your printer manufactures the physical object layer by layer.
If you've ever used a word processor: an STL file is like a document. Your slicer is like a printer driver. Your 3D printer is the printer.
What Does STL Stand For?
STL stands for **Stereolithography** — named after the first commercial 3D printing process. The name is historical; the format is now used for all types of FDM/FFF printing.
Some people also say it stands for "Standard Triangle Language" or "Standard Tessellation Language" — both of these are informal but accurate descriptions of how the format works.
How Does an STL File Work?
An STL file describes a 3D shape as a collection of triangles. Every surface of the model is covered by triangles (this mesh is called tessellation). The more triangles, the more detailed the model — but also the larger the file size.
When your slicer opens the file, it calculates how to build that shape by stacking thin horizontal layers of plastic on top of each other. Each layer is a slice of the model — which is why the software is called a "slicer."
What's the Difference Between STL and 3MF?
**3MF** is a newer format that's increasingly popular. It stores more information than STL:
Practical difference:
Bodhin Industries includes both formats where available. If you're on Bambu Studio or PrusaSlicer, the 3MF file will preserve the recommended print settings automatically.
What Software Opens STL Files?
Any slicer software opens STL files. The most common options:
All are free to download.
You can also open STL files in 3D modeling software (Blender, Fusion 360, TinkerCAD) if you want to modify the model before printing.
What Can You Do With an STL File?
1. **Print it** — load into slicer → slice → send to printer
2. **Scale it** — most slicers let you resize the model before printing
3. **Modify it** — open in Blender or Fusion 360 to customize
4. **Print multiple times** — buy once, print as many times as you want
5. **Sell the printed items** — if the license allows commercial use (Bodhin Industries licenses do)
What You Cannot Do With an STL File
You cannot resell, redistribute, or re-upload the digital file itself. You bought the right to print the file, not to sell the file. Check the specific license terms on each product.