What an ICO file is
An ICO file is a small container that holds the same icon at several sizes. Windows picks the size that fits each place, such as the title bar, the taskbar or a folder in large icon view. Browsers do the same with a favicon.ico file. Because one file carries many sizes, the icon stays crisp instead of being blurrily scaled from a single image. The ICO format page has more background.
How to use it
- Choose your image: PNG, JPG, SVG or any other format your browser can open. A square image with a transparent background gives the cleanest result.
- Tick the sizes to include: 16, 24, 32, 48, 64, 128 and 256 px are available. The default set is 16, 32, 48 and 256.
- If the image is not square, choose how to make it square. Fit centers the whole image on a transparent square; fill crops the middle so the image covers the whole square.
- Check the preview, which shows every selected size.
- Download the .ico file.
The icon is created in your browser, and the image you choose stays on your device.
Which sizes to include
| Size | Where it typically appears |
|---|---|
| 16 px | Browser tabs, title bars, small lists |
| 24 and 32 px | Taskbar and small icons, especially with display scaling |
| 48 px | Medium icons in File Explorer |
| 64 and 128 px | In-between sizes on high-resolution screens |
| 256 px | Large and extra large icon views |
The default set of 16, 32, 48 and 256 covers the common cases while keeping the file compact. Add 24 and 64 if the icon will often be seen on screens with scaling above 100 percent. For a favicon only, 16, 32 and 48 are plenty.
Designing for tiny sizes
An icon that looks great at 256 px can turn into a smudge at 16 px. Fine text, thin lines and small details disappear. Use a simple, bold shape with strong contrast, and keep the empty margin around it small so the shape fills the square. Check the 16 px preview before you download; if it is unreadable, simplify the source image or crop it tighter.
Technical note
Each size is stored inside the ICO as a PNG image. This keeps the file small and preserves transparency. PNG-based icons work in Windows Vista and later and in all current browsers; very old systems such as Windows XP cannot read them.
For a complete website icon set, with apple-touch-icon, Android sizes and the HTML code, use the favicon generator instead. Our guide on how to make a favicon explains which files a site needs.
Frequently asked questions
Can I use the ICO file as a website favicon?
Yes. Name it favicon.ico and place it in the root folder of your site. Most sites also add PNG icons for phones and tablets, which the favicon generator creates for you.
Is a transparent background kept?
Yes. Every size is stored as PNG, which keeps transparency. In fit mode, the space added around a non-square image is transparent too.
Why does my icon look blurry at 16 px?
The image has too much detail for such a small grid. Simplify it, increase the contrast, or use a version of your logo designed for small sizes.
Can I start from an SVG logo?
Yes. SVG files are accepted and rendered at each selected size. If you need large PNG versions of the same logo, SVG to PNG can produce them.