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Image MIME Reference
AVCS

AVC Image Sequence (HEIF Container)

image/avcs
VS

Computer Graphics Metafile

image/cgm
CGM

A complete technical comparison of AVC Image Sequence (HEIF Container) and Computer Graphics Metafile — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

Equal browser support

Feature Support

Feature AVCS CGM
Transparency (Alpha) Yes Yes
Animation Support Yes ✕ No
Progressive Loading ✕ No ✕ No
HDR Support Yes ✕ No
EXIF Metadata Yes ✕ No
ICC Color Profile Yes Yes
AVC Image Sequence (HEIF Container)
image/avcs
Extension
.avcs.heifs
Container HEIF / ISOBMFF (ISO/IEC 14496-12)
Compression Lossy / Lossless
Algorithm
AVC (Advanced Video Coding / H.264)
Color Depth 8-bit, 10-bit, 12-bit
Developed by Moving Picture Experts Group (MPEG) / ISO/IEC JTC 1
Released 2015
Magic Bytes
XX XX XX XX 66 74 79 70 61 76 63 73
Full AVCS reference →
Computer Graphics Metafile
image/cgm
Extension
.cgm
Container CGM
Compression Uncompressed / Binary / Character / Clear Text
Algorithm
Deflate (in some WebCGM profiles)
Color Depth 8-bit, 16-bit, 24-bit, 32-bit
Developed by ISO / IEC
Released 1987
Magic Bytes
00 20 (Binary) / 42 45 47 49 4E 20 4D 45 54 41 46 49 4C 45 (Clear Text)
Full CGM reference →

Browser Support Comparison

Browser AVCS CGM
Chrome Chrome
✕ ✕
Firefox Firefox
✕ ✕
Safari Safari
✕ ✕
Edge Edge
✕ ✕
IE IE (Legacy)
✕ ✕
AVCS

AVCS Strengths

  • Efficiently stores bursts of images or animations utilizing inter-frame compression
  • Leverages the highly compatible and widely hardware-accelerated AVC (H.264) codec
  • Robust HEIF container supports extensive metadata, alpha channels, and depth maps
Limitations
  • Zero native support in web browsers
  • Largely superseded in efficiency by newer sequence formats like HEICS (HEVC) or Animated AVIF (AV1)
  • Complicated container structure requires specialized parsing libraries
CGM

CGM Strengths

  • Strictly standardized by ISO, ensuring long-term archiving and cross-platform compatibility in engineering
  • Excellent support for rich metadata, hyperlinks, and technical hotspots via the WebCGM profile
  • Can store complex 2D geometry, rasters, and text in a single lightweight file
Limitations
  • Multiple encoding schemes (Binary, Character, Clear Text) make parser development difficult
  • Zero native support in modern web browsers without third-party plugins
  • Largely replaced by SVG for general-purpose 2D vector graphics on the web

When to choose which format

AVCS
Use AVCS when…
  • Burst Photography
  • Short Animations
  • Camera Capture
  • Archival Storage
CGM
Use CGM when…
  • Technical Illustrations
  • Aerospace & Defense (S1000D)
  • CAD/CAM
  • Geophysics

More comparisons

AVCS vs ACES → CGM vs ACES → AVCS vs APNG → CGM vs APNG → AVCS vs AVCI → CGM vs AVCI → AVCS vs AVIF → CGM vs AVIF → All comparisons →
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