FILE FORMAT GUIDE
STL File (.STL): What It Is & How to Open It
An STL file represents a three-dimensional surface as triangular facets. It is used in workflows such as 3D printing and can be stored as ASCII text or binary data. Import it into a mesh application to inspect the geometry; the extension alone does not tell you which encoding the file uses.
Quick facts
- Extension
- .stl
- Format
- STereoLithography
- Category
- 3d
- MIME type
- Not reviewed
- Standard / developer
- 3D Systems
- Open with
- Blender
What is STL?
STL describes surface geometry rather than a full editable CAD model. Its triangle-based representation has ASCII and binary variants. It does not provide a general texture or material system. A file may need geometry repair before downstream use; recognizing its format does not validate its printability.
How to open STL
BlenderWindows / macOS / Linux
Import the file using Blender's STL import support to inspect the mesh.
Common uses and compatibility
- Exchange triangular surface geometry
- Prepare mesh-based 3D printing workflows
Things to check
- Not a replacement for an editable CAD source model.
- Format identification does not validate mesh quality.
Technical details
- Signature
- Not reviewed
- Encoding
- ASCII or binary
- Container
- Not reviewed
- Compression
- Not reviewed
Public specification: not reviewed.
Sources & review
Sources reviewed 2026-09-18.