Free webp to jpg
EN
Image MIME Reference
APNG

Animated Portable Network Graphics

image/vnd.mozilla.apng
VS

SealedMedia SoftSeal JPEG

image/vnd.sealedmedia.softseal.jpg
SoftSeal-JPEG

A complete technical comparison of Animated Portable Network Graphics and SealedMedia SoftSeal JPEG — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

APNG wins on browser support

Feature Support

Feature APNG SoftSeal-JPEG
Transparency (Alpha) Yes ✕ No
Animation Support Yes ✕ No
Progressive Loading Yes ✕ No
HDR Support ✕ No ✕ No
EXIF Metadata Yes ✕ No
ICC Color Profile Yes ✕ No
Animated Portable Network Graphics
image/vnd.mozilla.apng
Extension
.apng.png
Container PNG Chunk Stream
Compression Deflate (Lossless)
Algorithm
Deflate (zlib)
Color Depth 8-bit (Indexed), 24-bit (TrueColor), 32-bit (RGBA)
Developed by Mozilla Corporation (Stuart Parmenter & Vladimir Vukićević)
Released 2004
Magic Bytes
89 50 4E 47 0D 0A 1A 0A
Full APNG reference →
SealedMedia SoftSeal JPEG
image/vnd.sealedmedia.softseal.jpg
Extension
.sjpg.sealed-jpg.sealed-jpeg
Container SealedMedia SoftSeal Wrapper
Compression Encrypted Payload (DCT)
Algorithm
AES EncryptionDiscrete Cosine Transform (Internal JPEG payload)
Color Depth Encrypted Payload (Historically 24-bit RGB)
Developed by SealedMedia (Acquired by Oracle Corporation)
Released Late 1990s
Magic Bytes
Unknown (Proprietary SealedMedia Container)
Full SoftSeal-JPEG reference →

Browser Support Comparison

Browser APNG SoftSeal-JPEG
Chrome Chrome
✓ 59
 ✕
Firefox Firefox
✓ 3
 ✕
Safari Safari
✓ 8
 ✕
Edge Edge
✓ 79
 ✕
IE IE (Legacy)
✕ ✕
APNG

APNG Strengths

  • Supports 8-bit alpha transparency, completely solving the ugly 'white halo' problem inherent to GIFs
  • Gracefully degrades; viewers that do not support APNG will render a perfectly valid, static PNG of the first frame
  • Provides lossless compression that retains absolute pixel-perfect quality for UI elements and line art
Limitations
  • Because it relies on lossless Deflate compression, file sizes for complex, video-like animations can be massive compared to lossy formats like WebP or AVIF
  • Was initially rejected by the official PNG group, delaying its adoption for nearly a decade
  • Lacks native hardware decoding acceleration, unlike video-based animated formats (like MP4 or WebM)
SoftSeal-JPEG

SoftSeal-JPEG Strengths

  • Offered persistent document security; if a sensitive photo was emailed outside the company, it remained encrypted and unviewable without server authentication
  • Administrators possessed the ability to remotely revoke viewing rights to a specific image globally at any time
Limitations
  • Completely proprietary and relies on a central authentication server; if the server goes offline or the product is deprecated, the image is permanently inaccessible
  • Zero support in modern operating systems, web browsers, or standard image editing suites without heavy enterprise client installations
  • Oracle effectively discontinued the IRM product line, stranding many legacy sealed documents

When to choose which format

APNG
Use APNG when…
  • High-Quality Web Animations
  • Stickers (Apple iMessage, LINE, Discord)
  • UI Loaders with Alpha Transparency
  • GIF Replacement
SoftSeal-JPEG
Use SoftSeal-JPEG when…
  • Enterprise Information Rights Management (IRM)
  • Secure Distribution of Sensitive Photography
  • Revocable Corporate Document Access

More comparisons

APNG vs ACES → SoftSeal-JPEG vs ACES → APNG vs AVCI → SoftSeal-JPEG vs AVCI → APNG vs AVCS → SoftSeal-JPEG vs AVCS → APNG vs AVIF → SoftSeal-JPEG vs AVIF → All comparisons →
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