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Image MIME Reference
DjVu

DjVu Document

image/vnd.djvu
VS

Windows Icon (Legacy MIME)

image/x-icon
ICO

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

ICO wins on browser support

Feature Support

Feature DjVu ICO
Transparency (Alpha) Yes Yes
Animation Support ✕ No ✕ No
Progressive Loading Yes ✕ No
HDR Support ✕ No ✕ No
EXIF Metadata ✕ No ✕ No
ICC Color Profile ✕ No ✕ No
DjVu Document
image/vnd.djvu
Extension
.djvu.djv
Container Interchange File Format (IFF)
Compression JB2 (Bi-tonal Text) / IW44 (Wavelet Background) / BZZ (General Data/Text)
Algorithm
JB2IW44BZZ
Color Depth 1-bit (Foreground Text), 24-bit (Background)
Developed by AT&T Labs (Yann LeCun, Léon Bottou, Patrick Haffner, Paul G. Howard)
Released 1996
Magic Bytes
41 54 26 54 46 4F 52 4D
Full DjVu reference →
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 →

Browser Support Comparison

Browser DjVu ICO
Chrome Chrome
✕
✓ 1
Firefox Firefox
✕
✓ 1
Safari Safari
✕
✓ 1
Edge Edge
✕
✓ 12
IE IE (Legacy)
✕
✓
DjVu

DjVu Strengths

  • Unmatched compression ratios for high-resolution scanned documents (often 5 to 10 times smaller than equivalent JPEG/TIFF-based PDFs)
  • Separates text layers cleanly from backgrounds, allowing for highly legible text even at low file sizes
  • Embedded OCR (Optical Character Recognition) text layers allow for fast searching
Limitations
  • Lacks native support in modern operating systems and web browsers, requiring third-party software
  • Largely superseded by PDF/A and modern PDF compression standards in standard corporate workflows
  • Not suitable for vector graphics or born-digital documents (like Word exports), where standard PDF is far superior
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

When to choose which format

DjVu
Use DjVu when…
  • Scanned Books and Manuals
  • Digital Libraries (e.g., Internet Archive)
  • Historical Document Archiving
ICO
Use ICO when…
  • Website Favicons (favicon.ico)
  • Windows Application Executable Icons (.exe)
  • Desktop Shortcut Icons

More comparisons

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