What is a DWG File?

DWG File Format Overview

A DWG file (pronounced "drawing") is a binary file format used to store 2D and 3D design data and metadata. The name "DWG" is derived from the word "drawing." DWG files are the standard output of AutoCAD, the world's most popular CAD software developed by Autodesk.

When you receive a file with the .dwg extension, it typically contains architectural floor plans, mechanical engineering drawings, electrical schematics, site plans, or 3D models created in AutoCAD or a compatible CAD application.

DWG files are used by over 10 million CAD professionals worldwide, making it one of the most important file formats in engineering and architecture.

History of the DWG Format

The DWG format has a long history spanning over four decades:

• 1970s: The DWG format was originally created by Mike Riddle for his Interact CAD program
• 1982: Autodesk licensed the format and used it as the native format for AutoCAD 1.0
• 1990s: DWG became the industry standard as AutoCAD dominated the CAD market
• 1998: The Open Design Alliance (ODA) began reverse-engineering DWG for interoperability
• 2000s: Cloud-based and web-based DWG viewers emerged, making the format more accessible
• 2010s-Present: DWG support expanded to mobile devices, web browsers, and third-party applications

Today, DWG remains the dominant format in the AEC (Architecture, Engineering, and Construction) industry, with billions of DWG files in existence worldwide.

What Does a DWG File Contain?

A DWG file stores multiple types of data in a structured binary format:

• Geometric data: Lines, arcs, circles, polylines, splines, and other 2D/3D primitives that make up the drawing
• Layers: Organizational layers that group entities by type (walls, doors, electrical, plumbing, etc.)
• Blocks: Reusable collections of entities (furniture symbols, title blocks, standard components)
• Dimensions: Annotative dimensions with leaders, tolerances, and measurement values
• Text and MText: Single-line and multi-line text annotations with formatting
• Hatches: Fill patterns for cross-sections, material representations, and area fills
• External references (Xrefs): Links to other DWG files for modular design
• Viewports: Layout views for printing with different scales and orientations
• 3D objects: Solids, surfaces, meshes, and 3D face entities
• Metadata: File properties, creation date, last modified date, and custom properties

DWG File Versions

Each major release of AutoCAD may introduce a new DWG file version. The version determines which features are supported and which software can read the file. Major versions include:

Most modern DWG viewers and converters support versions from AC1015 (AutoCAD 2000) onward. Older versions (pre-2000) may require specialized tools.

How to Open a DWG File

There are several ways to open DWG files, depending on whether you need to edit or just view them:

Online Viewers (No Installation)

• DWG Viewer Online — Open DWG files instantly in your browser with 3D orbit, measurement tools, and layer controls. No signup, no upload.
• Autodesk Viewer — Web-based viewer from Autodesk (requires an Autodesk account)

Desktop Software

• AutoCAD — Full editing capabilities (subscription required)
• DWG TrueView — Viewing and version conversion from Autodesk (no editing)
• LibreCAD — Open-source 2D CAD application (limited DWG support via DXF conversion)
• BricsCAD — Full DWG-compatible CAD application
• nanoCAD — DWG-compatible CAD with a no-cost tier

Mobile Apps

• AutoCAD Mobile — View and edit DWG on iOS and Android
• DWG FastView — Lightweight DWG viewer for mobile devices

For a detailed walkthrough, see our guide on how to open DWG files without AutoCAD.

Frequently Asked Questions