Free webp to jpg
EN
Image MIME Reference
ICO

Windows Icon (Legacy MIME)

image/x-icon
VS

Adobe Photoshop Document

image/vnd.adobe.photoshop
PSD

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

ICO wins on browser support

Feature Support

Feature ICO PSD
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 →
Adobe Photoshop Document
image/vnd.adobe.photoshop
Extension
.psd.psb.pdd
Container Adobe Photoshop Document (PSD/PSB)
Compression Uncompressed / RLE (Run-Length Encoding) / ZIP
Algorithm
RLEZIP (with or without prediction)None
Color Depth 1-bit (Bitmap), 8-bit, 16-bit, 32-bit (Float/HDR)
Developed by Adobe Systems
Released 1990
Magic Bytes
38 42 50 53
Full PSD reference →

Browser Support Comparison

Browser ICO PSD
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
PSD

PSD Strengths

  • The undisputed global standard for layered raster graphics and non-destructive image editing
  • Supports incredibly complex compositions combining raster data, vector shapes, live text, and adjustment layers
  • Full support for advanced color spaces (CMYK, Lab, multi-channel) and 32-bit floating-point HDR workflows
Limitations
  • Proprietary format: while the specification is published, complete feature-parity is rarely achieved by third-party software (e.g., smart objects and complex layer styles often break)
  • Files can reach enormous sizes (gigabytes) due to the preservation of unflattened, high-resolution layer data
  • Zero support for native rendering in web browsers or standard mobile image viewers

When to choose which format

ICO
Use ICO when…
  • Website Favicons (favicon.ico)
  • Windows Application Executable Icons (.exe)
  • Desktop Shortcut Icons
PSD
Use PSD when…
  • Professional Photo Retouching
  • Digital Painting and Illustration
  • UI/UX Design Workflows
  • Graphic Design and Print Production

More comparisons

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