WebP to ICO Converter

Windows icons and the classic favicon.ico must be ICO files, but artwork increasingly comes as WebP. This converter draws your WebP at each icon size you tick — scaling down in steps so small sizes stay crisp — and writes one multi-size .ico with the transparency kept. Optional classic BMP entries make small sizes readable by Windows XP and old programs. Everything runs in your browser.

How to use this tool

1. Choose a WebP image, ideally square and at least 256 × 256 px with a transparent background.
2. Tick the sizes: 16, 32 and 48 for a favicon; add 256 for Windows desktop icons.
3. Choose how a non-square picture is made square.
4. Download the .ico.

Formula

ICO = 6-byte header (0, type 1, count) + one 16-byte entry per size (width and height, where 0 means 256; 1 plane; 32 bits per pixel; byte length; offset) + the images, each stored as PNG or as a classic 32-bit bitmap with a 1-bit mask.

Every size is drawn from the original WebP, halving the image step by step before the last resize so 16 px icons are not jagged. Animated WebP uses its first frame. Browsers accept favicon.ico with 16, 32 and 48 px images; Windows uses 256 px for large desktop icons.

Example

An icon with only the 16 px size as a classic entry is exactly 1,150 bytes: 6 + 16 bytes of directory, a 40-byte header, 16 × 16 × 4 = 1,024 bytes of colour and 16 × 4 = 64 bytes of mask. The default set (16, 32, 48 and 256 px, all PNG) is usually a few tens of kilobytes for a simple logo.