ICO

ICO is the format Windows uses for application and file-type icons. A single .ico file is a container that can hold multiple versions of the same image at different resolutions and color depths (e.g., 16×16 at 8-bit and 256×256 at 32-bit with alpha), allowing Windows to pick the most appropriate version for each display context. ICO files are also used as favicons — the small icon displayed in browser tabs — although modern browsers additionally accept PNG and SVG for this purpose.

File extensions	.ico
MIME type	image/x-icon
Developer	Microsoft
First released	1985
Category	Images
Open standard	No (proprietary)

What opens ICO files

• Microsoft Windows (natively, as application/system icons)
• Adobe Photoshop (with plugin)
• GIMP
• IcoFX

Browse File Formats

Reference details for 53 file formats — extensions, MIME types, what opens each one, and how they convert.

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