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Image MIME Reference
AVCI

AVC Image (HEIF Container)

image/avci
VS

AVC Image Sequence (HEIF Container)

image/avcs
AVCS

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

Equal browser support

Feature Support

Feature AVCI AVCS
Transparency (Alpha) Yes Yes
Animation Support ✕ No Yes
Progressive Loading ✕ No ✕ No
HDR Support Yes Yes
EXIF Metadata Yes Yes
ICC Color Profile Yes Yes
AVC Image (HEIF Container)
image/avci
Extension
.avci.hif
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 69
Full AVCI reference →
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 →

Browser Support Comparison

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

AVCI Strengths

  • Shares the robust, flexible HEIF container architecture that allows for rich metadata, HDR, and depth maps.
  • Backed by the highly ubiquitous AVC (H.264) codec, which is widely supported in hardware decoding.
  • Supports rectangular cropping and rotation metadata without needing to re-encode the pixel data.
Limitations
  • No native support within web browsers for HTML rendering.
  • Inferior compression efficiency when compared to newer container formats like HEIC (HEVC) or AVIF (AV1).
  • Easily confused with HEIC and AVIF, which use the same base ISOBMFF container.
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  • Largely superseded in efficiency by newer sequence formats like HEICS (HEVC) or Animated AVIF (AV1)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

When to choose which format

AVCI
Use AVCI when…
  • Digital Photography
  • Camera Capture
  • Archival Storage
AVCS
Use AVCS when…
  • Burst Photography
  • Short Animations
  • Camera Capture
  • Archival Storage

More comparisons

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