What is an ICO Icon?
An ICO file is an image file format used for computer icons in Microsoft Windows. ICO files contain one or more small images at multiple sizes and color depths, such that they can be scaled appropriately.
Example ICO icon (Google favicon shown here)
ICO files typically appear in browser tabs, bookmarks, and when websites are saved to the desktop.
Key Features of ICO Format:
- Supports multiple sizes within a single file (16x16, 32x32, 48x48, etc.)
- Includes transparency (alpha channel) support
- Native support in all web browsers
- Traditional format for Windows application icons
How to Implement ICO Icons in Your Website
1. Basic Implementation (Favicon)
The most common use of ICO icons is as a favicon for your website. Place this code in the <head> section of your HTML:
<link rel="icon" href="/favicon.ico" type="image/x-icon">
Implementation Notes:
- The
favicon.icofile should be placed in your website's root directory - Browsers will automatically look for
/favicon.icoeven without this tag - For best results, include multiple sizes (16x16, 32x32, 48x48) in your ICO file
2. Advanced Implementation with Multiple Icons
For better control across different devices and contexts, you can specify multiple icon formats:
<!-- Basic ICO favicon --> <link rel="icon" href="/favicon.ico" type="image/x-icon"> <link rel="shortcut icon" href="/favicon.ico" type="image/x-icon"> <!-- High resolution icons --> <link rel="icon" type="image/png" href="/favicon-32x32.png" sizes="32x32"> <link rel="icon" type="image/png" href="/favicon-16x16.png" sizes="16x16"> <!-- Apple Touch Icon --> <link rel="apple-touch-icon" sizes="180x180" href="/apple-touch-icon.png"> <!-- Windows 8/10 Tile Icon --> <meta name="msapplication-TileImage" content="/mstile-144x144.png">
Note: While ICO is the traditional format, modern browsers also support PNG for favicons. The ICO format remains important for backward compatibility.
Best Practices for ICO Icons
1. File Placement
Always place your favicon.ico file in the root directory of your website. This ensures:
- Browsers can find it automatically
- Bookmarks and shortcuts will display your icon properly
- Search engines and social media platforms can access it
2. Multiple Sizes
Your ICO file should include these standard sizes for different use cases:
- 16x16 - Browser tabs and address bars
- 32x32 - Taskbar shortcuts and desktop icons
- 48x48 - Windows Explorer views
- 64x64 - High DPI displays
3. Design Considerations
- Keep designs simple - complex details won't be visible at small sizes
- Use high contrast colors for visibility
- Test your icon at all sizes to ensure readability
- Consider creating a square design with transparent background
Browser Support
ICO format has excellent browser support across all platforms:
| Browser | Support | Notes |
|---|---|---|
| Chrome | Yes | Full support |
| Firefox | Yes | Full support |
| Safari | Yes | Full support |
| Edge | Yes | Full support |
| Internet Explorer | Yes | Version 5+ |
| Opera | Yes | Full support |
Pro Tip: While ICO is universally supported, modern browsers also support PNG favicons. For best results, provide both formats.
Troubleshooting Common Issues
1. Icon Not Displaying
If your icon isn't appearing:
- Verify the file is named
favicon.icoand placed in the root directory - Clear your browser cache (Ctrl+F5 or Cmd+Shift+R)
- Check the file permissions on your server
- Ensure the ICO file contains at least a 16x16 image
2. Icon Appears Blurry
For crisp icons:
- Include higher resolution versions (32x32, 64x64) in your ICO file
- Design your icon at 256x256 and scale down
- Avoid thin lines and small text
3. Icon Doesn't Update
When changing your favicon:
- Use a different filename or append a query string (
favicon.ico?v=2) - Wait - some browsers cache icons for extended periods
- Test in multiple browsers