Free webp to jpg
EN
Image MIME Reference
ICO

Windows Icon (Legacy MIME)

image/x-icon
VS

QuickTime Image Format

image/x-quicktime
QTIF

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

ICO wins on browser support

Feature Support

Feature ICO QTIF
Transparency (Alpha) Yes Yes
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 →
QuickTime Image Format
image/x-quicktime
Extension
.qtif.qti.qif
Container QuickTime Atom Container
Compression Varies (JPEG, SMC, Apple Video, Cinepak, Uncompressed)
Algorithm
QuickTime Image Compression Manager (ICM) Codecs
Color Depth 1-bit to 32-bit (Varies depending on the enclosed codec)
Developed by Apple Computer, Inc.
Released 1991
Magic Bytes
Varies (Typically begins with a 32-bit size integer followed by 69 64 73 63 ('idsc'))
Full QTIF reference →

Browser Support Comparison

Browser ICO QTIF
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
QTIF

QTIF Strengths

  • Extremely flexible architecture allowing it to encapsulate virtually any image compression algorithm available on the host machine
  • Supported 32-bit images with alpha channels (transparency) long before PNG became an established standard
Limitations
  • Fundamentally tied to Apple's deprecated QuickTime architecture, rendering the files almost entirely unreadable on modern systems without specialized legacy software or FFmpeg
  • The 'wrapper' nature of the format means that even if a parser can read the QTIF container, it may fail to render the image if it lacks the specific proprietary codec (like Apple SMC) used to compress the pixel data
  • Zero native support in modern web browsers

When to choose which format

ICO
Use ICO when…
  • Website Favicons (favicon.ico)
  • Windows Application Executable Icons (.exe)
  • Desktop Shortcut Icons
QTIF
Use QTIF when…
  • Classic Mac OS Applications and Backgrounds
  • QuickTime VR Panorama Textures
  • 1990s CD-ROM Multimedia Assets

More comparisons

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