ICO file (Windows Icon)
Windows / favicon icon. Written as a multi-size PNG icon bundle.
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Convert ICO to JPG, free and without uploading it.
What is an ICO file?
In short: An ICO file (.ico) is an image file in the ICO format. An ICO file is a bundle rather than a single image: it holds the same icon at several sizes, so the system can pick the right one for a taskbar, a title bar or a desktop shortcut without scaling anything. It can be converted to JPG, PNG or WEBP for free in a web browser with iHateFiles, without uploading it.
The Windows icon format, present since Windows 1.0 in 1985 and later adopted by browsers for favicons.
An ICO file is a bundle rather than a single image: it holds the same icon at several sizes, so the system can pick the right one for a taskbar, a title bar or a desktop shortcut without scaling anything. Modern ICO files store each size as an embedded PNG.
What ICO is good at
- Several sizes in one file, so nothing is scaled badly
- The one format every browser accepts at /favicon.ico
- Transparency throughout
Where ICO falls short
- Only useful at icon sizes
- Not a general image format
- Very old readers only understand a handful of specific sizes
When to use ICO
Use ICO for a website favicon and for Windows application icons. Include 16, 32 and 48 pixel versions at minimum.
How to open an ICO file
Windows and every browser. Image editors vary in how well they write one.
| Windows | Windows shows ICO files as icons rather than opening them. IrfanView or GIMP will show the individual sizes inside. |
|---|---|
| macOS | Preview opens it and shows the largest size only. |
| Linux | GIMP reads and writes every size in the file. |
| Phone | Not practical without a dedicated app. |
| In a browser | Browsers display ICO — that is what a favicon is. |
The thing that usually goes wrong
Renaming a PNG to favicon.ico works in most browsers and then fails in the one that matters. A real ICO bundle avoids the argument entirely.
Not sure the file really is an ICO? Identify it by its contents, whatever its extension says.
Questions
What is an ICO file?
ICO stands for Windows Icon. Windows / favicon icon. Written as a multi-size PNG icon bundle. Files use the .ico extension.
What does ICO stand for?
ICO stands for Windows Icon. ICO is short for icon.
How do I open an ICO file?
On Windows: Windows shows ICO files as icons rather than opening them. IrfanView or GIMP will show the individual sizes inside. On a Mac: Preview opens it and shows the largest size only. On a phone: Not practical without a dedicated app. Or convert an ICO here to a format that opens everywhere, free and without uploading it.
Can I convert ICO for free?
Yes. Every conversion here is free and unlimited, because your own device does the work rather than a server we have to pay for.
Is ICO lossless?
Yes. ICO stores every pixel exactly, at the cost of a larger file.