The format Windows has used since 1985
ICO is old. Really old. It predates the web, it predates JPEG, it predates PNG. And somehow, it’s still the standard for Windows application icons, desktop shortcuts, and the classic favicon.ico that browsers look for automatically. You can’t ship a Windows app without one. You can’t have a universally compatible favicon without one.
This tool takes any image, PNG, JPEG, WebP, and produces a proper ICO file containing 16x16, 32x32, and 48x48 pixel versions bundled together. One file, three sizes, ready for browser tabs, Windows taskbars, and desktop shortcuts.
Creating your ICO
- Upload a square image (256x256 or larger works best).
- Preview it.
- Click “Convert to ICO & Download”.
That’s it. The tool automatically scales your source to all three sizes and bundles them into a single multi-resolution ICO file. Drop it in your website root as favicon.ico and browsers find it automatically, no <link> tag required (though adding one is still best practice).
What’s inside the ICO
- 16x16: browser tabs, small icon view in Windows Explorer
- 32x32: high-DPI browser tabs, Windows desktop shortcuts at standard scaling
- 48x48: Windows taskbar, medium icon view
- Transparency support: if your source PNG has an alpha channel, it carries over
- Multi-size bundling: all three versions live in a single file, and Windows picks the right one automatically
Where ICO files are non-negotiable
The favicon.ico convention. Every browser since IE5 has looked for a file called favicon.ico in the website root. It’s the oldest, most reliable way to get your icon into browser tabs. Modern alternatives exist (PNG favicons, SVG favicons), but the ICO file is the guaranteed fallback.
Windows desktop application development. Building a .exe? The icon must be ICO format. Period. Windows won’t accept PNG or SVG for application icons. Your installer, your taskbar button, your desktop shortcut, all ICO.
Desktop shortcuts and batch scripts. You’ve written a PowerShell script your team uses daily. Giving it a custom ICO icon makes it findable in a sea of identical default icons on the desktop.
Bookmark bar icons. When a user bookmarks your site, the favicon shows up in their bookmark bar. ICO provides the crispest result across the widest range of browsers and OS versions.
One important tip: start with a square image. Non-square sources get squeezed to fit a square frame, and the distortion is not flattering. Simple, high-contrast designs work best, complex artwork with fine detail turns into an unreadable blob at 16x16 pixels.
If you need a complete favicon package with six sizes plus both PNG and ICO formats, the Favicon Generator covers that in one download. The Image Resizer can help prepare your source image before conversion.
ICO questions
What sizes end up in the file?
16x16, 32x32, and 48x48: the three most commonly needed icon sizes for web and Windows use. The ICO format bundles all three into one file.
Does my source image need to be square?
Strongly recommended. Icons display in square frames everywhere, browser tabs, taskbars, desktops. A rectangular source will be scaled to fit the square, which usually looks awkward.
ICO vs. PNG for favicons, which should I use?
Both, ideally. ICO gives you legacy compatibility (every browser, every version, guaranteed). PNG favicons are cleaner for modern browsers. Most developers include both: a favicon.ico in the root plus <link> tags pointing to PNG versions.
Does this preserve transparency?
Yes. If your source image is a PNG with a transparent background, the ICO output will have transparency too.
Can I just rename a PNG to .ico?
Technically some browsers might accept it, but it’s not a valid ICO file. ICO has its own format structure with embedded bitmap data. This tool creates a proper ICO that works everywhere.