---
title: ".step file — what it is and how to open it"
description: "A .step file is a STEP 3D Model. The neutral ISO format for exchanging solid 3D models between CAD systems. How to open one on Windows, macOS and Linux, and what to convert it to."
url: https://atoneplace.net/file/step/
site: "At One Place"
---

# .step files

**.step file: STEP 3D Model**

The neutral ISO format for exchanging solid 3D models between CAD systems.

## What opens a .step file

- **Windows:** FreeCAD, Autodesk Fusion, SolidWorks, eDrawings Viewer
- **macOS:** FreeCAD, Autodesk Fusion, eDrawings Viewer
- **Linux:** FreeCAD, OpenSCAD (via import), gmsh
- **In a browser:** Autodesk Viewer, Onshape

## What a .step file is

STEP (ISO 10303) stores true solid geometry — surfaces, dimensions and assembly structure — rather than a mesh of triangles, so a model stays editable when it moves between SolidWorks, Fusion 360 and FreeCAD. Files are plain text, which makes them large but inspectable. The extension is also written .stp; both are the same format.

## Converting it

A .step file is commonly converted to .stl, .iges, .obj, .3mf or .dwg. It is a plain text format, so any text editor can open and edit it directly.

## Details

- **Extension:** .step
- **Full name:** STEP 3D Model
- **Category:** CAD
- **MIME type:** model/step
- **Created by:** ISO 10303
- **Format:** Plain text

## Common questions

### How do I open a .step file?

On Windows use FreeCAD; on macOS use FreeCAD; on Linux use FreeCAD. The neutral ISO format for exchanging solid 3D models between CAD systems.

### What is a .step file?

STEP 3D Model. STEP (ISO 10303) stores true solid geometry — surfaces, dimensions and assembly structure — rather than a mesh of triangles, so a model stays editable when it moves between SolidWorks, Fusion 360 and FreeCAD. Files are plain text, which makes them large but inspectable.

### Can I convert a .step file?

Yes. It is usually converted to .stl, .iges, .obj, .3mf or .dwg, either by exporting from one of the programs listed above or with a format converter.

## Related pages

- [.dwg — AutoCAD Drawing](https://atoneplace.net/file/dwg/)
- [.dxf — Drawing Exchange Format](https://atoneplace.net/file/dxf/)

## Sources

- Media Types Registry — IANA (https://www.iana.org/assignments/media-types/)
- Official vendor product documentation — At One Place (/about/)