Image MIME Reference
NAPLPS
North American Presentation Level Protocol Syntax
image/naplps
VS
X Window Dump (Legacy MIME Alias)
image/x-xwindowdump
XWD
A complete technical comparison of North American Presentation Level Protocol Syntax and X Window Dump (Legacy MIME Alias) — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.
Equal browser support
Feature Support
| Feature | NAPLPS | XWD |
|---|---|---|
| Transparency (Alpha) | ✕ No | Yes |
| Animation Support | Yes | ✕ No |
| Progressive Loading | Yes | ✕ No |
| HDR Support | ✕ No | ✕ No |
| EXIF Metadata | ✕ No | ✕ No |
| ICC Color Profile | ✕ No | ✕ No |
North American Presentation Level Protocol Syntax
image/naplps
Extension
.nap.naplps
Container
NAPLPS Byte Stream
Compression
Uncompressed (Tokenized ASCII Commands)
Algorithm
None (Coordinate encoding)
Color Depth
16-color palette (Indexed from larger color spaces)
Developed by
ANSI / CSA (Based on Canadian CRC's Telidon)
Released
1983
Magic Bytes
1B (Variable / ESC sequences)
X Window Dump (Legacy MIME Alias)
image/x-xwindowdump
Extension
.xwd.wd
Container
XWDHeader / XWDFileHeader Structure
Compression
Uncompressed
Algorithm
None
Color Depth
8-bit (Indexed), 16-bit (High Color), 24-bit (True Color), 32-bit (True Color with Alpha/Padding)
Developed by
MIT / X Consortium (X Window System)
Released
1987
Magic Bytes
00 00 00 64 (Typically indicates a 100-byte header size followed by version)
Browser Support Comparison
| Browser | NAPLPS | XWD |
|---|---|---|
Chrome
|
✕ | ✕ |
Firefox
|
✕ | ✕ |
Safari
|
✕ | ✕ |
Edge
|
✕ | ✕ |
IE (Legacy)
|
✕ | ✕ |
NAPLPS
NAPLPS Strengths
- Extremely bandwidth-efficient, enabling colorful graphical interfaces over early 300 baud dial-up connections
- Resolution-independent vector scaling allowed the exact same file to be displayed accurately on varied early PC monitors and television sets
Limitations
- Completely obsolete and unsupported by modern web technologies
- Relies heavily on stateful parsing and terminal emulators rather than straightforward file decoding
- Easily misidentified by MIME sniffers as plain text or generic binary streams due to the lack of a standardized file header
XWD
XWD Strengths
- Provides an exact, raw pixel dump directly from the X11 display server memory without compression overhead
- Extremely fast for Unix environments to generate during low-level graphical debugging
Limitations
- Completely uncompressed, resulting in large, bloated file sizes
- Zero support in web browsers or modern desktop environments without specialized graphics translation tools
- Verbose legacy MIME strings like 'image/x-xwindowdump' require backend normalization in modern applications
When to choose which format
NAPLPS
Use NAPLPS when…
- 1980s Videotex Services
- Prodigy Online Service Graphics
- Historical BBS Terminal Graphics
- Legacy Teletext Broadcasts
XWD
Use XWD when…
- X Window System (X11) Display Debugging and Screenshots
- Legacy Unix/Linux System Administration