ICO vs PNG Favicon
Complete comparison of ICO and PNG favicon formats. Learn which format is right for your website.
What is ICO?
ICO (Windows Icon) is the traditional favicon format, originally created for Microsoft Windows. It's been the de facto standard for favicons since the early days of the web.
ICO files can contain multiple icon resolutions in a single file, which browsers automatically select the appropriate size from. This was advantageous when bandwidth was limited and multi-file support wasn't standardized.
While modern browsers still support ICO, they've largely moved toward PNG for new implementations due to PNG's superior color support and compression.
What is PNG?
PNG (Portable Network Graphics) is a modern image format that supports full 24-bit color (16.7 million colors) and alpha channel transparency.
For favicons, PNG offers superior quality compared to ICO, especially at small sizes. PNG's lossless compression maintains detail without artifacts, and the alpha channel provides smooth, anti-aliased edges.
Modern browsers (Chrome, Firefox, Safari, Edge) fully support PNG favicons. Most modern web projects use PNG as the primary favicon format, with ICO provided as a fallback for older browsers.
ICO Format: Pros & Cons
Advantages
- Widely supported by all browsers, including older versions
- Can contain multiple resolutions in a single file
- Native format for Windows desktop shortcuts
- Automatic fallback for browsers that prefer ICO
Disadvantages
- Limited color palette in older versions (256 colors)
- Larger file size compared to PNG for equivalent quality
- No transparency support in legacy implementations
- Limited scalability compared to vector formats
PNG Format: Pros & Cons
Advantages
- Full 24-bit color support with millions of colors
- Alpha channel for smooth transparency
- Smaller file size for better loading performance
- Better quality at small sizes due to compression
- Modern web standard with excellent browser support
Disadvantages
- Not a true multi-resolution format (need separate files)
- Legacy browsers might not recognize PNG as favicon
- Requires multiple files for different sizes
When to Use Each Format
Here's a quick guide to help you decide:
Use ICO When
Supporting legacy browsers (IE9 and older), Windows desktop shortcuts, or when you need a single file format.
Use PNG When
Targeting modern browsers, prioritizing image quality, supporting transparency, or building progressive web apps.
Best Practice: Use Both
For maximum browser compatibility, use both formats:
Provide PNG as Primary
Use PNG for modern browsers (favicon-32x32.png, favicon-16x16.png)
Include ICO as Fallback
Add favicon.ico for legacy browsers and Windows support
Let Browsers Choose
Modern browsers will automatically select the PNG format, while older browsers fall back to ICO
Technical Details
Quick technical comparison between formats:
Color Support
ICO: Up to 16-bit (65,536 colors) in modern versions, 8-bit (256 colors) in legacy
PNG: 24-bit (16.7 million colors)
Transparency
ICO: Binary transparency (1-bit) or alpha channel in modern versions
PNG: Full alpha channel (smooth transparency)
Compression
ICO: Uncompressed or PNG-based compression
PNG: Lossless compression (DEFLATE algorithm)
File Size
ICO: Generally larger due to multiple resolutions
PNG: Smaller due to efficient compression
Bottom Line
For most modern websites, PNG is the superior favicon format. It offers better quality, smaller file sizes, and excellent browser support.
However, providing both formats (with PNG as the primary and ICO as a fallback) ensures maximum compatibility while maintaining modern standards. Favicon Tools automatically generates both formats when you create your favicon package.