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Image MIME Reference
BMP

Windows Bitmap (Legacy Windows MIME Alias)

image/x-windows-bmp
VS

AutoCAD Drawing

image/vnd.dwg
DWG

A complete technical comparison of Windows Bitmap (Legacy Windows MIME Alias) and AutoCAD Drawing — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

BMP wins on browser support

Feature Support

Feature BMP DWG
Transparency (Alpha) Yes Yes
Animation Support ✕ No ✕ No
Progressive Loading ✕ No ✕ No
HDR Support ✕ No ✕ No
EXIF Metadata ✕ No ✕ No
ICC Color Profile Yes ✕ No
Windows Bitmap (Legacy Windows MIME Alias)
image/x-windows-bmp
Extension
.bmp.dib
Container DIB (Device-Independent Bitmap)
Compression Uncompressed / Run-Length Encoding (RLE)
Algorithm
NoneRLE4RLE8
Color Depth 1-bit (Monochrome), 4-bit (16 colors), 8-bit (256 colors), 16-bit (High Color), 24-bit (True Color), 32-bit (True Color with Alpha)
Developed by Microsoft Corporation
Released 1985
Magic Bytes
42 4D
Full BMP reference →
AutoCAD Drawing
image/vnd.dwg
Extension
.dwg
Container DWG Binary Container
Compression Proprietary Binary Compression (LZ77 based in newer versions)
Algorithm
Proprietary (Autodesk ObjectDBX)
Color Depth Vector (True Color / Indexed AutoCAD Color Index)
Developed by Autodesk
Released 1982
Magic Bytes
41 43 31 30 (AC10)
Full DWG reference →

Browser Support Comparison

Browser BMP DWG
Chrome Chrome
✓ 1
 ✕
Firefox Firefox
✓ 1
 ✕
Safari Safari
✓ 1
 ✕
Edge Edge
✓ 12
 ✕
IE IE (Legacy)
✓
 ✕
BMP

BMP Strengths

  • Universally supported by all major operating systems and modern web browsers
  • Maintains perfect, lossless fidelity because pixel data is stored without lossy compression artifacts
Limitations
  • Massive file size overhead due to a lack of modern compression algorithms
  • Legacy MIME strings like 'image/x-windows-bmp' can trigger validation warnings in strict security or API environments if unhandled
DWG

DWG Strengths

  • The undisputed industry standard for 2D drafting and basic 3D CAD modeling
  • Highly optimized binary structure keeps file sizes relatively small compared to text-based CAD formats like DXF
  • Supports incredibly complex datasets including external references (XREFs), dynamic blocks, and extensive custom metadata
Limitations
  • It is a closed, proprietary format, making it difficult for third-party developers to support fully without licensing the Open Design Alliance (ODA) SDK
  • Lacks native web or standard operating system previewer support
  • Format versions change frequently (roughly every 3 years), breaking backward compatibility for older CAD software

When to choose which format

BMP
Use BMP when…
  • Legacy Windows Desktop Registry Associations
  • Older Enterprise Intranet Applications
  • Windows Graphics Archival
DWG
Use DWG when…
  • Architectural Floor Plans
  • Mechanical Engineering Models
  • Civil Engineering Drafts
  • 3D Product Designs

More comparisons

BMP vs ACES → DWG vs ACES → BMP vs APNG → DWG vs APNG → BMP vs AVCI → DWG vs AVCI → BMP vs AVCS → DWG vs AVCS → BMP vs AVIF → DWG vs AVIF → All comparisons →
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