Free webp to jpg
EN
Image MIME Reference
ICO

Windows Icon (Legacy MIME)

image/x-icon
VS

Simple Vector Format

image/vnd.svf
SVF

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

ICO wins on browser support

Feature Support

Feature ICO SVF
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 →
Simple Vector Format
image/vnd.svf
Extension
.svf
Container Custom Binary/Text (Legacy) or ZIP (Autodesk Forge)
Compression Uncompressed / Deflate (in modern Autodesk SVF implementations)
Algorithm
None
Color Depth Vector Data (Not Applicable)
Developed by SoftSource & NCSA (National Center for Supercomputing Applications)
Released 1995
Magic Bytes
Unknown (SoftSource SVF)
Full SVF reference →

Browser Support Comparison

Browser ICO SVF
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
SVF

SVF Strengths

  • Acted as a crucial pioneering stepping-stone in proving that scalable, zoomable vector graphics were viable and necessary for the World Wide Web
Limitations
  • Completely obsolete and unsupported by modern web standards
  • Required end-users to install bulky, proprietary browser plugins
  • Causes significant developer confusion today due to Autodesk adopting the exact same acronym and file extension for a completely different technology

When to choose which format

ICO
Use ICO when…
  • Website Favicons (favicon.ico)
  • Windows Application Executable Icons (.exe)
  • Desktop Shortcut Icons
SVF
Use SVF when…
  • Historical Web-based CAD Viewers (1990s)
  • Legacy 2D Vector Archival
  • Autodesk Platform Services (Forge) Model Translation (Name Collision)

More comparisons

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