Free webp to jpg
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Image MIME Reference
PNG

Portable Network Graphics (Legacy MIME)

image/x-png
VS

X Bitmap (Legacy MIME Alias)

image/x-xbm
XBM

A complete technical comparison of Portable Network Graphics (Legacy MIME) and X Bitmap (Legacy MIME Alias) — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

PNG wins on browser support

Feature Support

Feature PNG XBM
Transparency (Alpha) Yes Yes
Animation Support ✕ No ✕ No
Progressive Loading Yes ✕ No
HDR Support Yes ✕ No
EXIF Metadata Yes ✕ No
ICC Color Profile Yes ✕ No
Portable Network Graphics (Legacy MIME)
image/x-png
Extension
.png
Container PNG Chunk Structure (IHDR, IDAT, IEND)
Compression Deflate (Lossless)
Algorithm
Deflate (LZ77)
Color Depth 1-bit to 16-bit (Grayscale), 8-bit (Indexed Palette), 24-bit (True Color), 32-bit (True Color with Alpha), 48-bit (High Color), 64-bit (High Color with Alpha)
Developed by PNG Development Group
Released 1996
Magic Bytes
89 50 4E 47 0D 0A 1A 0A
Full PNG reference →
X Bitmap (Legacy MIME Alias)
image/x-xbm
Extension
.xbm
Container C Source Code Header (.h)
Compression Uncompressed (Source Code)
Algorithm
None
Color Depth 1-bit (Monochrome)
Developed by MIT / X Consortium (X Window System)
Released 1988
Magic Bytes
23 64 65 66 69 6e 65 (ASCII '#define')
Full XBM reference →

Browser Support Comparison

Browser PNG XBM
Chrome Chrome
✓ 1
 ✕
Firefox Firefox
✓ 1
 ✕
Safari Safari
✓ 1
 ✕
Edge Edge
✓ 12
 ✕
IE IE (Legacy)
✓
✓
PNG

PNG Strengths

  • The underlying format provides flawless, lossless compression and perfect 8-bit alpha channel transparency
  • Universally supported by every modern operating system, image editor, and web browser
Limitations
  • The 'image/x-png' string is an obsolete vendor quirk that forces backend developers to write redundant normalization logic in file upload scripts
  • If left unnormalized, strict MIME validators or content security policies on modern systems may incorrectly reject valid PNG files
XBM

XBM Strengths

  • Can be compiled directly into C or C++ source code without needing an external file loader or binary asset manager
  • Human-readable structure allows developers to inspect, edit, or hand-craft tiny icons directly within a text editor
  • Extremely predictable and lightweight for 1-bit hardware displays and embedded systems
Limitations
  • Strictly limited to 1-bit monochrome (black and white) graphics with no gray or color support
  • Text-based C syntax creates massive file bloat compared to binary 1-bit formats like PBM
  • Completely deprecated in modern web browsers and desktop GUI frameworks

When to choose which format

PNG
Use PNG when…
  • Legacy Internet Explorer File Uploads
  • Older ASP/PHP Web Applications
  • Lossless Web Graphics
XBM
Use XBM when…
  • X Window System (X11) Cursors and Icons
  • Embedded C/C++ Firmware UI Assets
  • Early 1990s Unix Web Graphics

More comparisons

PNG vs ACES → XBM vs ACES → PNG vs APNG → XBM vs APNG → PNG vs AVCI → XBM vs AVCI → PNG vs AVCS → XBM vs AVCS → PNG vs AVIF → XBM vs AVIF → All comparisons →
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