Image format
What is a ICO file?
ICO is the Windows icon container format — it can bundle several sizes of the same image into one file for favicons and app icons.
ICO was built for exactly one job: giving Windows a single file that holds several resolutions and color depths of the same icon, so the operating system can pick whichever version fits — a small taskbar icon versus a large desktop shortcut, for instance — without any scaling. That same trick is why browsers still expect a site's favicon.ico to work the same way: one file, several embedded sizes, used at whatever resolution the browser tab needs.
How to open a ICO file
ICO files open readily in Windows Explorer previews it automatically, Any web browser. For real editing rather than just viewing, reach for GIMP, IcoFX, Photoshop (with a plugin).
Strengths & limitations
Good for
- multi-resolution support in a single file
- the format browsers expect for favicon.ico
Watch out for
- not meant for anything beyond small icons
Convert ICO files
Orbfile can convert ICO both ways, entirely in your browser — pick a direction below:
Frequently asked questions
What does a ICO file contain?+
ICO is the Windows icon container format — it can bundle several sizes of the same image into one file for favicons and app icons.
Can I convert ICO for free?+
Yes — Orbfile's image converter handles ICO for free, with no file limit, watermark, or account, and it runs entirely in your browser.
Is converting a ICO file safe and private?+
Yes. Orbfile processes ICO files locally on your device using WebAssembly — nothing is uploaded to a server, so there's nothing to leak or store.
Who created the ICO format?+
ICO was developed by Microsoft, first released around 1990.
Browse the full file format guide.