Free webp to jpg
EN
Image MIME Reference
ICO

Windows Icon (Legacy MIME)

image/x-icon
VS

GIMP Image Format

image/x-xcf
XCF

A complete technical comparison of Windows Icon (Legacy MIME) and GIMP 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 XCF
Transparency (Alpha) Yes Yes
Animation Support ✕ No Yes
Progressive Loading ✕ No ✕ No
HDR Support ✕ No Yes
EXIF Metadata ✕ No Yes
ICC Color Profile ✕ No Yes
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 →
GIMP Image Format
image/x-xcf
Extension
.xcf
Container GIMP Hierarchical Chunk Container
Compression None / RLE (Run-Length Encoding) / Zlib / Deflate (In newer GIMP versions)
Algorithm
NoneRLEZlib
Color Depth 8-bit per channel, 16-bit per channel, 32-bit floating point
Developed by Spencer Kimball, Peter Mattis, and the GIMP Development Team
Released 1995
Magic Bytes
67 69 6D 70 20 78 63 66
Full XCF reference →

Browser Support Comparison

Browser ICO XCF
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
XCF

XCF Strengths

  • Preserves all non-destructive editing elements, layer hierarchies, masks, and alpha channels across GIMP sessions
  • Open and thoroughly documented specification within the open-source community, allowing third-party tools like Krita and ImageMagick to read project files
  • Reliable magic byte header prevents misidentification
Limitations
  • Massive file sizes because raw, unflattened layer bitmaps and masks are stored directly within the project archive
  • Completely proprietary to the GIMP ecosystem for deep editing; cannot be natively rendered or parsed by web browsers
  • Third-party software supporting XCF may occasionally struggle to render complex text layer adjustments or advanced layer blend modes identically to GIMP

When to choose which format

ICO
Use ICO when…
  • Website Favicons (favicon.ico)
  • Windows Application Executable Icons (.exe)
  • Desktop Shortcut Icons
XCF
Use XCF when…
  • GIMP Native Project Archival
  • Layered Photo Editing and Graphic Design
  • Intermediary Asset Preparation for Export

More comparisons

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