What is the ICO format?
a container format for favicons and Windows icons
- MIME type
- image/x-icon
- Extensions
- .ico
- Introduced
- 1985
- Compression
- Lossless compression
- Transparency
- Yes
- Animation
- No
- Shown directly in browsers
- Yes
- On this site
- Read (input) · Save (output)
Overview
ICO is the format used for Windows icons and website favicons. Its distinguishing feature is that one file can hold several sizes, such as 16×16, 32×32 and 256×256.
This site packs PNG data scaled to at most 256×256 into an ICO container. Images that aren't square are centered with their aspect ratio preserved, and the leftover area is left transparent.
History
ICO is the icon file format that goes back to Windows 1.0 (1985). Early icons held only small bitmaps, but since Windows Vista it can embed PNG data directly, which allows high-resolution 256×256 icons.
On the web, it became the de facto standard for site icons (favicons) after Internet Explorer introduced favicon.ico around 1999.
Pros
- The standard favicon format
- Supports transparency
- Can hold multiple sizes in one file
Cons
- Limited to 256×256
- Unsuitable for ordinary photos
Best used for
- Website favicons
- Windows program icons
Compatibility
Every browser recognizes it as a favicon, and Windows Explorer can use it as an icon directly.
Convert ICO
Convert from ICO
Convert to ICO
ICO: frequently asked questions
+Which programs can open ICO files?
Every browser recognizes it as a favicon, and Windows Explorer can use it as an icon directly.
+Does ICO support transparent backgrounds?
Yes, ICO supports transparent backgrounds.
+How do I convert ICO to another format?
Upload your ICO file to AnyPicToAnyPic and pick one of PNG, JPG, WebP, GIF, BMP, SVG. It is converted right in your browser and the file is never uploaded.