DwgIO is a .NET library and command line tool that reads Autodesk AutoCAD drawings (.dwg) directly from disk, without AutoCAD or the AutoCAD API, and exports their metadata and contents to JSON.

What it does

• Detects the DWG version of a file, from AC1012 (R13) to AC1032 (R2018).
• Opens the container of AutoCAD 2004 and later drawings (AC1018, AC1024, AC1027, AC1032): file header, page map, section map and compressed data pages, with optional checksum verification.
• Reads named sections (AcDb:Header, AcDb:AcDbObjects, ...) as decompressed bytes.
• Parses drawing metadata: summary information with custom properties and dates, application information, file dependencies and the embedded thumbnail preview.
• Lists the objects of a drawing through its handle map and decodes the geometry of LINE, CIRCLE, ARC and POINT entities.
• Writes a JSON export of the metadata, the section catalog and the decoded entities.

Install

Install the command line tool:

dotnet tool install --global DwgIO.Cli

and add the library to a .NET project:

dotnet add package DwgIO

The library targets .NET 8 and .NET 10. It uses managed code without native dependencies or Windows-only APIs and supports Windows, Linux and macOS. Tests currently run on Windows.

Command line

Print the version, metadata, object and entity summary and section table of a drawing:

dwgio inspect drawing.dwg

Export metadata, the section catalog and the decoded entities to JSON:

dwgio drawing.dwg drawing.json

Write the decompressed bytes of one named section:

dwgio extract drawing.dwg AcDb:Header header.bin

Save the embedded thumbnail preview. Without an extension, .png, .wmf or .bmp is added to match the image:

dwgio preview drawing.dwg thumbnail

Errors go to standard error.

Exit codes

Code	Meaning
0	The command succeeded.
1	The command line is wrong.
2	The input file does not exist.
3	The DWG version is not supported yet (R13 to R2000, R2007) or not recognised.
4	The file could not be parsed, the drawing has no thumbnail preview (preview), or an unexpected error occurred.

Library

Open a drawing, list its sections and read one of them:

using System;
using DwgIO;

var doc = DwgDocument.Open("drawing.dwg");

Console.WriteLine($"{doc.Version.Release} ({doc.Version.Magic})");

foreach (var section in doc.Sections)
{
    Console.WriteLine($"{section.Name,-24} {section.Size,12} bytes  pages={section.PageCount}");
}

byte[] header = doc.ReadSection("AcDb:Header");

foreach (var entity in doc.Entities)
{
    Console.WriteLine(entity);
}

DwgDocument.Open throws FileNotFoundException for a missing file, DwgUnsupportedVersionException for a version whose container is not implemented yet, and DwgException for a damaged or truncated file. The library writes nothing to the console: parts of a drawing that could not be decoded are listed in DwgDocument.Diagnostics. DwgReaderOptions selects what is read and turns on checksum verification (VerifyChecksums).

The JSON export is DwgJsonExporter in the DwgIO.Json namespace. See Getting started and Public API for the supported types.

The documentation site with the API reference is at https://ioextend.github.io/DwgIO/. offers an automatically generated overview of the repository.

Status

Area	Status
Version detection (AC1012 to AC1032)	done
AutoCAD 2004 and later container (AC1018, AC1024, AC1027, AC1032): file header, page map, section map, data pages	done
Decompression of section data	done
Checksum verification (file header CRC-32, data page checksums)	done
AcDb:SummaryInfo parsing (metadata, custom properties, dates)	done
Reading named sections (AcDb:Header, AcDb:AcDbObjects, ...)	done
AcDb:AppInfo, AcDb:FileDepList and AcDb:Preview parsing	done
Handle map and object stream inventory	done
Entity decoding: LINE, CIRCLE, ARC and POINT geometry	done (partial)
AutoCAD 2007 container (AC1021)	planned
R13 to R2000 container (AC1012 to AC1015)	planned

Supported versions

Magic	Release	Container	Status
AC1012	R13	flat section locators	planned
AC1014	R14	flat section locators	planned
AC1015	R2000	flat section locators	planned
AC1018	R2004	paged, compressed sections	done
AC1021	R2007	Reed-Solomon coded pages	planned
AC1024	R2010	paged, compressed sections	done
AC1027	R2013	paged, compressed sections	done
AC1032	R2018	paged, compressed sections	done

Limitations

• Version 0.4.0 is a preview. The API can change before 1.0.
• Drawings saved as R13 to R2000 or R2007 are refused (DwgUnsupportedVersionException, exit code 3).
• Entity geometry is decoded for LINE, CIRCLE, ARC and POINT only. Other entities are listed as objects without geometry, and entity bodies that could not be decoded are recorded in DwgDocument.Diagnostics.
• There is no support for writing or modifying DWG files.

Build from source and tests

Use the .NET SDK selected by global.json, which specifies 10.0.401 with latestFeature roll-forward.

From the repository root:

dotnet build DwgIO.slnx -c Release
dotnet test

Tests requiring real DWG files are skipped with a message unless DWGIO_TEST_FILES or a test_files folder provides private drawings. The repository includes no DWG drawings. See test fixtures.

Contributing

See CONTRIBUTING.md and the Code of Conduct. Release changes are recorded in CHANGELOG.md.

Security

Report vulnerabilities through GitHub private vulnerability reporting in the repository's Security tab. Do not open public issues for security vulnerabilities. See SECURITY.md.

License and trademarks

DwgIO is licensed under the MIT License.

Autodesk, AutoCAD and DWG are registered trademarks or trademarks of Autodesk, Inc. DwgIO is not affiliated with, endorsed by or sponsored by Autodesk.

The file format is read by analysing files for interoperability. No Autodesk code or binaries are used or included.