Image MIME Reference
DDS
DirectDraw Surface
image/vnd.ms-dds
VS
SealedMedia Portable Network Graphics
image/vnd.sealed.png
Sealed-PNG
A complete technical comparison of DirectDraw Surface 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 | DDS | Sealed-PNG |
|---|---|---|
| Transparency (Alpha) | Yes | ✕ No |
| Animation Support | ✕ No | ✕ No |
| Progressive Loading | ✕ No | ✕ No |
| HDR Support | Yes | ✕ No |
| EXIF Metadata | ✕ No | ✕ No |
| ICC Color Profile | ✕ No | ✕ No |
DirectDraw Surface
image/vnd.ms-dds
Extension
.dds
Container
DirectDraw Surface
Compression
Block Compression (BC1-BC7) / DXTC / S3TC / Uncompressed (RGBA, Floating-Point)
Algorithm
DXT1-DXT5BC1-BC7ASTC / ETC2 (Extended)
Color Depth
8-bit, 16-bit, 24-bit, 32-bit (RGBA), 16-bit/32-bit Floating Point (HDR)
Developed by
Microsoft Corporation
Released
1999
Magic Bytes
44 44 53 20
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)
Browser Support Comparison
| Browser | DDS | Sealed-PNG |
|---|---|---|
Chrome
|
✕ | ✕ |
Firefox
|
✕ | ✕ |
Safari
|
✕ | ✕ |
Edge
|
✕ | ✕ |
IE (Legacy)
|
✕ | ✕ |
DDS
DDS Strengths
- Massively reduces VRAM footprint and memory bandwidth usage because the GPU decodes the block compression in hardware
- Encapsulates complex texture arrays, volume textures, cubemaps, and entire mipmap chains within a single, highly structured file
- Supports high-dynamic-range (HDR) floating-point data for modern physically based rendering (PBR)
Limitations
- Block compression algorithms (like DXT) are lossy and can introduce ugly blocky artifacts, especially in smooth gradients or normal maps if not tuned properly
- Files are generally larger on the physical hard drive than highly compressed formats like PNG or WebP
- Zero support in web browsers or standard consumer image viewers
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
DDS
Use DDS when…
- Real-Time 3D Game Textures
- DirectX and Vulkan Rendering Pipelines
- Skyboxes and Environment Cubemaps
- Volume Textures (3D Textures)
Sealed-PNG
Use Sealed-PNG when…
- Enterprise Information Rights Management (IRM)
- Secure Corporate Intellectual Property Distribution
- Revocable Medical or Legal Imaging