Free webp to jpg
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Image MIME Reference
Sealed-PNG

SealedMedia Portable Network Graphics

image/vnd.sealed.png
VS

Wireless Bitmap

image/vnd.wap.wbmp
WBMP

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

Equal browser support

Feature Support

Feature Sealed-PNG WBMP
Transparency (Alpha) ✕ No ✕ No
Animation Support ✕ No ✕ No
Progressive Loading ✕ No ✕ No
HDR Support ✕ No ✕ No
EXIF Metadata ✕ No ✕ No
ICC Color Profile ✕ No ✕ No
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 →
Wireless Bitmap
image/vnd.wap.wbmp
Extension
.wbmp
Container WBMP Type 0
Compression Uncompressed
Algorithm
None
Color Depth 1-bit (Monochrome)
Developed by WAP Forum (Now Open Mobile Alliance)
Released 1999
Magic Bytes
00 00
Full WBMP reference →

Browser Support Comparison

Browser Sealed-PNG WBMP
Chrome Chrome
✕ ✕
Firefox Firefox
✕ ✕
Safari Safari
✕ ✕
Edge Edge
✕ ✕
IE IE (Legacy)
✕ ✕
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
WBMP

WBMP Strengths

  • Extremely low processing overhead made it perfectly suited for the ultra-low-power CPUs of late 1990s mobile devices
  • Tightly integrated into the WML (Wireless Markup Language) stack, enabling the first functional mobile internet experiences
Limitations
  • Completely obsolete and lacks support in modern operating systems and browsers
  • Limited entirely to 1-bit black and white (0 for black, 1 for white) with zero support for grayscale, color, or transparency
  • The lack of a strong file header signature makes automated MIME type detection highly unreliable

When to choose which format

Sealed-PNG
Use Sealed-PNG when…
  • Enterprise Information Rights Management (IRM)
  • Secure Corporate Intellectual Property Distribution
  • Revocable Medical or Legal Imaging
WBMP
Use WBMP when…
  • Legacy WML (Wireless Markup Language) Mobile Sites
  • Early Mobile Phone Icons and Operator Logos
  • Historical WAP Archival

More comparisons

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