ICO (Windows Icon) is a multi-resolution container format that embeds multiple images at standard sizes like 16x16, 32x32, 48x48, and 256x256 pixels within a single file. ICO files are used for Windows application icons and website favicons. BMP (Bitmap) is the simplest uncompressed raster format, storing raw pixel data that any image viewer or editor can open. Converting ICO to BMP extracts the largest embedded image from the ICO container and saves it as a flat, uncompressed bitmap.

This conversion is useful when you need to edit, inspect, or use an icon image in applications that do not understand the ICO multi-resolution container format. Most image editors, web platforms, and design tools cannot open ICO files directly but handle BMP without any issues.

ICO is a specialized format understood only by Windows shell, web browsers (for favicons), and a few icon editors. When you need to view, edit, or repurpose an icon image in a standard image editor like Photoshop, GIMP, or Paint.NET, converting to BMP provides the most straightforward uncompressed representation of the icon's pixel data.

BMP output is also useful for embedded systems, firmware, and legacy applications that need raw pixel data from icon images. Display controllers, boot screens, and custom OS shells that read BMP directly can use the extracted icon data without implementing ICO container parsing.

The ICO container is parsed to identify all embedded image entries and their resolutions. The largest resolution image (typically 256x256 for modern icons, or 48x48 for older icons) is extracted. If the 256x256 entry is stored as embedded PNG data (common in Windows Vista+ icons), it is decoded from PNG to raw pixels. Older ICO entries stored as BMP-format device-independent bitmaps are extracted directly. The pixel data is written as a standard Windows BMP v3 file with 24-bit (RGB) or 32-bit (RGBA) color depth. Alpha channel data from 32-bit ICO entries is preserved in the BMP output. Sharp handles the ICO decoding.

The largest resolution image in the ICO container is extracted. Modern icons typically include a 256x256 entry; older icons may have 48x48 as their maximum.

This conversion extracts the single largest resolution. To extract all embedded sizes, you would need a specialized ICO editor or image processing script.

Yes. 32-bit ICO entries with alpha transparency are converted to 32-bit BMP with alpha channel data. Some older image viewers may not display BMP alpha correctly.

ICO images are designed for icons, so their pixel dimensions are small (16x16 to 256x256). Even uncompressed, a 256x256 pixel BMP is only about 256 KB.

Yes. Website favicon.ico files are standard ICO format and are processed identically. The largest embedded image is extracted and saved as BMP.

Device	ICO	BMP
Windows PC	Native	Native
macOS	Partial	Partial
iPhone/iPad	Partial	Partial
Android	Partial	Partial
Linux	Partial	Partial
Web Browser	No	No

Feature	ICO	BMP
Full Name	Windows Icon	Bitmap Image
Extension	.ico	.bmp
Best For	Windows icons	Uncompressed

Convert ICO to BMP — Free Online Converter

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