ICO Converter

ICO (Icon) is a file format developed by Microsoft for storing icons in Windows applications and websites. Unlike regular image formats that contain a single image, an ICO file is a container that can hold multiple image resolutions in a single file — typically 16×16, 32×32, 48×48, and 64×64 pixels. When Windows or a web browser needs to display the icon, it selects the most appropriate size from the container. For websites, favicon.ico placed in the root directory has been the standard favicon mechanism since Internet Explorer 5. While modern browsers support PNG and SVG favicons, the ICO format remains important for backward compatibility. Internet Explorer (still used in some enterprise environments) only supports ICO favicons. Windows desktop shortcuts and application icons use ICO files. The format supports both 4-bit (16 colors), 8-bit (256 colors), and 32-bit (full color with alpha transparency) color depths, though modern usage is exclusively 32-bit for smooth edges and transparency.

A comprehensive favicon implementation requires multiple files and formats to cover all browsers and devices. The favicon.ico file (containing 16×16 and 32×32 versions) serves as the universal fallback — place it in your site root directory. Modern browsers prefer PNG favicons declared via link tags: a 32×32 PNG for desktop browser tabs and a 192×192 PNG for Android Chrome. Apple devices need a 180×180 Apple touch icon for home screen bookmarks, declared with <link rel="apple-touch-icon">. Progressive Web Apps (PWAs) require icons at 192×192 and 512×512 in the manifest.json file. To test your implementation, check the browser tab in Chrome, Safari, and Firefox, add a bookmark on iOS and Android to verify touch icons, and use Google's Lighthouse audit which flags missing favicon sizes. Common mistakes include only providing favicon.ico without PNG alternatives, forgetting the Apple touch icon, and serving icons that are too small for their intended use.