Convert to ICO

ICO files and why they require multiple sizes

An ICO file is a container that stores multiple versions of an icon at different resolutions within a single file. Web browsers request the favicon.ico from a website's root and choose the appropriate size based on context: 16x16 in browser tabs, 32x32 in taskbars and bookmark bars, and 48-256px in operating system menus and app panels. Providing a multi-size ICO ensures the icon looks sharp in every context rather than being upscaled from a single small source.

Windows application development requires ICO files for executable icons. The operating system selects the appropriate icon size based on the view mode in Explorer, the taskbar dimensions, and the display DPI setting. A multi-size ICO covering 16, 32, 48, and 256px handles all standard Windows display contexts without upscaling blur.

Starting from the right source

Start with a high-resolution square source image - at least 256x256 pixels. The converter downscales to create all required sizes. Starting from a small image and upscaling produces blurry icons at larger sizes, which is particularly visible at 256px in file explorers and application lists. Square source images also crop correctly at all sizes without unexpected aspect ratio distortion. If your source is rectangular, crop it to a 1:1 ratio first to ensure the icon fills each size evenly.