ICO vs PNG Favicon — Which Format to Use in 2025
Compare ICO and PNG favicon formats. Learn when to use each, browser compatibility differences, file size trade-offs, and the recommended modern approach.
Detailed Explanation
ICO vs PNG Favicon
The two main formats for favicons are ICO (the legacy standard) and PNG (the modern approach). Understanding when to use each helps you provide the best experience across all browsers.
ICO Format
The ICO (Windows Icon) format was the original favicon format and has unique properties:
- Multi-resolution: A single .ico file can contain multiple sizes (16x16, 32x32, 48x48)
- Universal support: Supported by every browser, including very old versions
- Convention: Browsers automatically look for
/favicon.icoat the root of any domain - No
<link>tag required: Browsers fetch/favicon.icoeven without an explicit reference
Limitations:
- Larger file sizes compared to individual PNGs
- No native transparency support in older ICO implementations
- Cannot include sizes larger than 256x256 efficiently
- Not suitable for Apple Touch Icons or PWA icons
PNG Format
PNG favicons are the modern standard:
- Better compression: Smaller file sizes at equivalent quality
- True alpha transparency: Full support for semi-transparent pixels
- Per-size optimization: Each size can be individually optimized
- Specified via
<link>tags: Explicit size declaration
<link rel="icon" type="image/png" sizes="32x32" href="/favicon-32x32.png">
<link rel="icon" type="image/png" sizes="16x16" href="/favicon-16x16.png">
Recommended Approach
The modern best practice is to use both:
- PNG files for all specific sizes via
<link>tags - A favicon.ico at the root as a fallback containing 16x16 and 32x32
This ensures universal compatibility while taking advantage of PNG benefits for modern browsers.
File Size Comparison
| Format | 16x16 | 32x32 | Combined |
|---|---|---|---|
| ICO (multi) | — | — | ~5-15 KB |
| PNG (each) | ~0.5-2 KB | ~1-3 KB | ~1.5-5 KB |
PNG files are typically 50-70% smaller than equivalent ICO files.
Use Case
This comparison is essential for any web developer making decisions about their favicon implementation strategy. Understanding the trade-offs between ICO and PNG helps balance backward compatibility with modern best practices, which is especially relevant for sites with diverse audience demographics.