CAD File Formats: DXF, DWG, STEP, and IGES for Non-Engineers
A practical guide to CAD file formats for developers, designers, and project managers who need to work with engineering files. Understand what each format contains and how to handle them.
Key Takeaways
- CAD files appear in web applications, data pipelines, and collaboration tools more often than many developers expect.
- DWG is Autodesk's native binary format — the dominant standard in architecture and civil engineering.
- STEP (Standard for the Exchange of Product Data) is the ISO standard for 3D solid model exchange.
- For web-based CAD viewing, convert STEP/DXF to glTF for 3D or SVG for 2D.
Why CAD Formats Matter Outside Engineering
CAD files appear in web applications, data pipelines, and collaboration tools more often than many developers expect. Manufacturing companies share STEP files with suppliers, architectural firms distribute DWG drawings, and 3D printing services accept multiple CAD formats. Understanding the basics helps you handle them correctly.
Format Overview
| Format | Type | Standard | Primary Use | Open? |
|---|---|---|---|---|
| DWG | 2D/3D | Autodesk proprietary | Architecture, mechanical | No |
| DXF | 2D/3D | Autodesk (documented) | CAD interchange | Partially |
| STEP (.stp) | 3D solid | ISO 10303 | Manufacturing exchange | Yes |
| IGES (.igs) | 3D surface | ANSI Y14.26M | Legacy exchange | Yes |
| Parasolid (.x_t) | 3D solid | Siemens | Solid modeling kernel | No |
DWG and DXF: The AutoCAD Ecosystem
DWG is Autodesk's native binary format — the dominant standard in architecture and civil engineering. DXF (Drawing Exchange Format) is the text-based interchange variant that most CAD software can read. When you receive DWG files but do not have AutoCAD, request DXF conversion or use open-source viewers.
STEP: The Universal 3D Exchange
STEP (Standard for the Exchange of Product Data) is the ISO standard for 3D solid model exchange. It preserves geometry, topology, and manufacturing information across different CAD systems. When a supplier sends you a 3D model, STEP is the safest format to request.
Handling CAD Files in Web Applications
For web-based CAD viewing, convert STEP/DXF to glTF for 3D or SVG for 2D. These web-native formats render in any browser without plugins. Libraries like Three.js can load converted models directly for interactive visualization.