Free webp to jpg
EN
Image MIME Reference
ICO

Windows Icon (Legacy MIME)

image/x-icon
VS

Wireless Bitmap

image/vnd.wap.wbmp
WBMP

A complete technical comparison of Windows Icon (Legacy MIME) and Wireless Bitmap — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

ICO wins on browser support

Feature Support

Feature ICO WBMP
Transparency (Alpha) Yes ✕ No
Animation Support ✕ No ✕ No
Progressive Loading ✕ No ✕ No
HDR Support ✕ No ✕ No
EXIF Metadata ✕ No ✕ No
ICC Color Profile ✕ No ✕ No
Windows Icon (Legacy MIME)
image/x-icon
Extension
.ico
Container ICO Directory Structure
Compression Uncompressed (DIB/BMP) / Deflate (Embedded PNG)
Algorithm
NoneDeflate (via PNG)
Color Depth 1-bit, 4-bit, 8-bit, 24-bit (True Color), 32-bit (RGBA)
Developed by Microsoft Corporation
Released 1985
Magic Bytes
00 00 01 00
Full ICO 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 ICO WBMP
Chrome Chrome
✓ 1
 ✕
Firefox Firefox
✓ 1
 ✕
Safari Safari
✓ 1
 ✕
Edge Edge
✓ 12
 ✕
IE IE (Legacy)
✓
 ✕
ICO

ICO Strengths

  • Universally supported by every web browser in existence for website favicons
  • Packs multiple resolutions into a single file, eliminating the need to serve different files for the taskbar vs. the desktop
  • Modern support for embedded PNGs (since Windows Vista) allows for excellent 32-bit transparency (alpha channels) and drastically reduced file sizes
Limitations
  • Internal file structure is convoluted due to decades of legacy cruft, such as the requirement for BMP data to lack a standard file header but double the height property for an archaic XOR/AND mask
  • Larger file size compared to a single optimized PNG or SVG, as it literally stores the same image multiple times at different scales
  • The MIME type landscape is highly fragmented (x-icon vs. vnd.microsoft.icon), causing occasional caching or strict-MIME validation errors on restrictive servers
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

ICO
Use ICO when…
  • Website Favicons (favicon.ico)
  • Windows Application Executable Icons (.exe)
  • Desktop Shortcut Icons
WBMP
Use WBMP when…
  • Legacy WML (Wireless Markup Language) Mobile Sites
  • Early Mobile Phone Icons and Operator Logos
  • Historical WAP Archival

More comparisons

ICO vs ACES → WBMP vs ACES → ICO vs APNG → WBMP vs APNG → ICO vs AVCI → WBMP vs AVCI → ICO vs AVCS → WBMP vs AVCS → ICO vs AVIF → WBMP vs AVIF → All comparisons →
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