Free webp to jpg
EN
Image MIME Reference
ICO

Windows Icon (Legacy MIME)

image/x-icon
VS

Scalable Vector Graphics

image/svg+xml
SVG

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

Equal browser support

Feature Support

Feature ICO SVG
Transparency (Alpha) Yes Yes
Animation Support ✕ No Yes
Progressive Loading ✕ No ✕ No
HDR Support ✕ No Yes
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 →
Scalable Vector Graphics
image/svg+xml
Extension
.svg.svgz
Container XML Document
Compression Uncompressed (Plain Text XML) / Lossless (GZIP via .svgz)
Algorithm
None (for .svg)GZIP (for .svgz)
Color Depth Vector (Independent of bit-depth), CSS Colors (HEX, RGB, HSL, Display-P3)
Developed by World Wide Web Consortium (W3C)
Released 2001
Magic Bytes
3C 73 76 67 (for <svg) / 3C 3F 78 6D 6C (for <?xml)
Full SVG reference →

Browser Support Comparison

Browser ICO SVG
Chrome Chrome
✓ 1
✓ All
Firefox Firefox
✓ 1
✓ All
Safari Safari
✓ 1
✓ All
Edge Edge
✓ 12
✓ All
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
SVG

SVG Strengths

  • Provides infinite resolution scalability, looking perfectly crisp on high-DPI (Retina) displays without increasing file size
  • Extremely lightweight compared to raster formats for flat graphics, logos, and UI elements
  • Can be manipulated dynamically via the browser's CSS and JavaScript engines (DOM integration)
Limitations
  • Unsuitable for complex photographic images or photorealistic textures
  • Poses critical security vulnerabilities (XSS and XML External Entity attacks) if user-uploaded SVGs are not heavily sanitized
  • Rendering performance degrades significantly if the SVG contains tens of thousands of complex nodes or deeply nested paths

When to choose which format

ICO
Use ICO when…
  • Website Favicons (favicon.ico)
  • Windows Application Executable Icons (.exe)
  • Desktop Shortcut Icons
SVG
Use SVG when…
  • Web Logos & UI Icons
  • Responsive Web Design Elements
  • Interactive Data Visualizations (D3.js)
  • CSS and SMIL Web Animations

More comparisons

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