What is .stl?

.stl (Stereolithography) is a 3D geometry format that represents surfaces using a collection of triangles. It is one of the most common formats for 3D printing and rapid prototyping, describing only the outer shell of an object without color, textures, or material properties.

This quick guide explains when to use .stl files, how to open them on any device, and how to share them instantly with FileXhost.

When to use .stl files

You are preparing models for 3D printing or rapid prototyping workflows.
You need a simple surface mesh representation without materials, textures, or animation.
You are exchanging solid models between CAD tools and slicer software for printing.
You want a widely supported format that many printers and services accept by default.

How to open .stl files

STL files can be opened in many 3D tools and 3D-printing applications, including Blender, FreeCAD, MeshLab, PrusaSlicer, Cura, and other slicer software. Most 3D printers and online printing services accept STL uploads directly. When you upload STL files to FileXhost, they can be shared as downloadable 3D assets that collaborators can inspect, repair, or slice for printing in their preferred tools.

Algorithm details

STL represents a 3D object's surface as a collection of triangular facets. Each triangle is defined by three vertices and a normal vector indicating its outward-facing direction. STL files can be stored in ASCII (human-readable text) or binary form, with binary being more compact and common in practice. The format does not store units, color, textures, or internal structure, so interpretation depends on the importing tool's settings and context.

Browser & platform support

Desktop: Browsers do not natively render STL files, but WebGL/WebGPU-based viewers and libraries can load them for interactive inspection.
Mobile: Mobile apps and web viewers can display STL models using embedded 3D engines or libraries; there is no built-in OS-level viewer.
OS: Operating systems typically rely on installed 3D viewers, CAD tools, or 3D-printing software to open STL files.

Format comparison

Feature	Details
Purpose	Designed primarily for describing printable 3D surfaces, making it a natural fit for 3D printing and rapid prototyping workflows.
Features	Stores only triangle meshes with vertex positions and normals; no materials, textures, colors, or animation data.
File Structure	ASCII STL uses text records for each triangle; binary STL uses a compact binary layout that is smaller and faster to parse.
Alternatives	OBJ, PLY, glTF, and 3MF provide richer metadata, color, or material support and may be better suited for visualization or modern pipelines.

How to create stl files

CAD Tools: Export STL from CAD software such as Fusion 360, SolidWorks, FreeCAD, and Tinkercad for 3D printing.
Modeling Tools: Export printable meshes from Blender or other modeling tools as STL for slicing.
Scanning/Photogrammetry: Some 3D scanning and reconstruction tools output STL meshes for printing or inspection.
Conversion Pipelines: Convert from richer formats like OBJ, glTF, or FBX into STL when preparing a final printable mesh.

How to convert stl files

FileXhost: Use FileXhost to distribute STL files so collaborators can download and convert them in their local tools.
Desktop: Use Blender, MeshLab, FreeCAD, or slicer software to convert STL into other mesh formats such as OBJ or PLY.
CLI: Use command-line utilities (e.g., mesh processing libraries, assimp-based tools) to batch-convert STL files.
Online Tools: Many web-based converters and repair services accept STL uploads and export alternative formats or fixed models.

Advantages & disadvantages

Advantages

Widely accepted standard for 3D printing and rapid prototyping
Simple triangle-based structure that most slicers and tools understand
ASCII and binary variants enable easy debugging or compact storage

Disadvantages

Does not store color, textures, or materials
Lacks units and metadata, which can cause scale confusion between tools
Not ideal as a general-purpose runtime format compared to glTF or OBJ

Tools & software

CAD/Modeling

Fusion 360, SolidWorks, FreeCAD, Blender, Tinkercad

Slicers/Printing

PrusaSlicer, Ultimaker Cura, Simplify3D, Bambu Studio

Viewers/Utilities

MeshLab, Windows 3D Viewer (on some systems), online STL viewers

Frequently asked questions

What is an STL file used for?

STL files are primarily used to describe the printable outer surface of 3D objects for 3D printing and rapid prototyping. They are the de facto standard for sending models to slicer software and many printing services.

What is the difference between ASCII and binary STL?

ASCII STL stores triangle data as human-readable text, while binary STL encodes the same information in a compact binary form. Binary STL files are usually much smaller and faster to load, but not directly readable in a text editor.

Should I use STL or OBJ for my model?

Use STL when your main goal is 3D printing and you only need the object's surface geometry. Use OBJ (or glTF/GLB) when you care about materials, textures, or broader visualization workflows.

Why does my STL print with the wrong scale or orientation?

STL does not store units or coordinate system metadata, so different tools may interpret the same file using different units or axes. Check your export settings and slicer configuration to ensure the intended scale and orientation.

Technical specs

File type: 3D
Extension: .stl
MIME type: model/stl, application/sla, application/octet-stream
Compression: Uncompressed
Max file size on FileXhost: Up to 25 MB per file on the free plan and up to 1 GB on Pro FileXhost accounts.

Upload your .stl file to FileXhost to get a clean, shareable URL in seconds. View the file in a modern browser, protect access with optional settings, and let others download it without any confusing ads or cluttered file pages.

Upload .stl file