Images

What is an ICO file?

Updated Jul 2026

Definition

ICO (Icon file) is the image format Windows uses for app icons and browser favicons. It can bundle several sizes of the same image into one file, and it supports transparency so icons sit cleanly over any background. Its main limitation is that almost nothing outside icon use treats it as a normal picture format.

ICOIcon file

Extension: .ico
Type: Images
Typically: Favicons, app icons
Transparency: Supported

Why ICO exists

The ICO format goes back to early Windows, where it was built specifically to hold the little pictures that represent programs, shortcuts, and files. Instead of storing one image, a single ICO file can hold multiple versions of the same icon at different sizes, like 16x16 for a taskbar and 256x256 for a desktop shortcut, so Windows can pick whichever fits the spot on screen.

In plain terms, an ICO is a small container of images rather than a single picture. That's why it works well for icons but poorly for anything else: photo viewers, editors, and websites are built around formats like PNG or JPG, not a multi-size container meant for system use.

People usually run into ICO in two spots: building or editing a favicon for a website, or trying to reuse a Windows app icon as a normal image. In both cases the ICO file needs converting to a PNG before most tools will do anything useful with it.

The trade-offs

Strengths

Can hold several icon sizes in one file
Supports transparency, so icons blend into any background
Lossless, so the image doesn't degrade from compression
Still the standard format for Windows app icons and favicons

Watch-outs

Not treated as a normal image by most photo and editing tools
Awkward to preview or edit without dedicated software
Rarely useful outside icon and favicon contexts
Usually needs converting to PNG before you can use it elsewhere

A note on privacy

ICO files are simple image containers and don't typically carry EXIF or location data the way a phone photo does. Still, if you're editing an app icon or building a favicon, uploading it to an online converter means that file leaves your machine for no real reason. Converting it on your own computer keeps the file, and whatever it's tied to, off someone else's server.

Convert an ICO file

Questions

How do I open an ICO file?

Windows shows it as an icon automatically. To actually view or edit it as a picture, you'll usually need to convert it to PNG first, since most image viewers don't handle ICO directly.

Is ICO better than PNG?

Not really, they serve different jobs. PNG is a general-purpose image format, while ICO exists specifically to bundle multiple icon sizes for Windows and favicons. For anything other than icons, PNG is the more usable choice.

Why does my app icon save as ICO?

Windows expects app and shortcut icons in ICO format because it can hold several sizes in one file. If you need that icon as a regular image, you'll want to convert it to PNG.

Can I convert ICO without uploading it?

Yes. A desktop app like Morphjet converts ICO to PNG or other formats right on your own computer, so the file never has to be sent anywhere online.

Can an ICO file have transparency?

Yes. ICO supports transparent backgrounds, which is why icons can appear to float over the desktop, taskbar, or a webpage without a visible box around them.

Morphjet opens and converts ICO and 1,800+ other formats, all on your own computer. Launching this July.