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Image MIME Reference
AVCS

AVC Image Sequence (HEIF Container)

image/avcs
VS

SealedMedia Portable Network Graphics

image/vnd.sealed.png
Sealed-PNG

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

Equal browser support

Feature Support

Feature AVCS Sealed-PNG
Transparency (Alpha) Yes ✕ No
Animation Support Yes ✕ No
Progressive Loading ✕ No ✕ No
HDR Support Yes ✕ No
EXIF Metadata Yes ✕ No
ICC Color Profile Yes ✕ No
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 →
SealedMedia Portable Network Graphics
image/vnd.sealed.png
Extension
.spng.sealed-png
Container SealedMedia / Oracle IRM Wrapper
Compression Encrypted Payload (Deflate)
Algorithm
AES EncryptionDeflate (Internal PNG payload)
Color Depth Encrypted Payload
Developed by SealedMedia (Acquired by Oracle Corporation)
Released Late 1990s / Early 2000s
Magic Bytes
Unknown (Proprietary SealedMedia Container)
Full Sealed-PNG reference →

Browser Support Comparison

Browser AVCS Sealed-PNG
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  • Largely superseded in efficiency by newer sequence formats like HEICS (HEVC) or Animated AVIF (AV1)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
Sealed-PNG

Sealed-PNG Strengths

  • Provided absolute control over intellectual property, allowing enterprise administrators to instantly revoke viewing rights of a local file globally
  • Detailed audit trails tracked exactly who opened the image, when, and from what IP address
Limitations
  • Completely proprietary and relies on a central authentication server; if the server goes offline, the image is permanently inaccessible
  • No support in modern operating systems, web browsers, or standard image editing software without installing heavy enterprise DRM clients
  • Oracle effectively deprecated the IRM product line, leaving legacy sealed documents difficult to recover

When to choose which format

AVCS
Use AVCS when…
  • Burst Photography
  • Short Animations
  • Camera Capture
  • Archival Storage
Sealed-PNG
Use Sealed-PNG when…
  • Enterprise Information Rights Management (IRM)
  • Secure Corporate Intellectual Property Distribution
  • Revocable Medical or Legal Imaging

More comparisons

AVCS vs ACES → Sealed-PNG vs ACES → AVCS vs APNG → Sealed-PNG vs APNG → AVCS vs AVCI → Sealed-PNG vs AVCI → AVCS vs AVIF → Sealed-PNG vs AVIF → All comparisons →
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