What an ICO file is
An ICO file is a container: one file that holds several square images of the same icon at different sizes. Whatever displays the icon picks the size that suits the space it has. A PNG, by contrast, is a single image at a single size, which is why converting means making several resized copies and packing them together.
On websites, the tab icon has traditionally been a file called favicon.ico in the site's root folder. Current browsers can also use PNG icons, but many sites still provide favicon.ico, and the HTML code this tool gives you includes it.
The sizes inside this ICO
| Size | What it's for |
|---|---|
| 16 × 16 px | The icon beside the page title in a browser tab |
| 32 × 32 px | The same tab icon on high-resolution screens, which draw it at double density |
| 48 × 48 px | A larger copy for places that show the icon bigger |
You can't add other sizes to the ICO. The larger icons a website needs, the 180 px Apple touch icon and the 192 and 512 px app icons, come as separate PNG files in the favicon package.
How transparency is kept
Each image inside the ICO is stored as a PNG with full transparency. The tool draws your picture onto an empty, transparent square at each size and adds no background, so a logo on a transparent PNG keeps smooth edges against a light or dark tab.
- Transparent PNG, SVG or WebP: transparent areas stay transparent at every size. The checkerboard preview and the light and dark tab previews show how it will look.
- JPG: a JPG can't be transparent, so its background, usually white, goes into the icon too, and shows as a white square on a dark tab. To avoid that, cut the logo out with Background Remover first and use the transparent PNG it gives you.
- Keep whole logo with a rectangular image: the space added above and below, or at the sides, is transparent, not white.
The Background colour and Padding settings only apply to the home-screen icons in the package (180, 192 and 512 px), because iPhones show black behind transparent areas. They don't change the ICO.
Getting a PNG ready for 16 pixels
A 16 × 16 px icon has only 256 pixels, so detail disappears quickly. A few things make a visible difference:
- Use a symbol, not a full logo. A single letter, a mark or the simplest part of your logo reads far better than a name written out in full.
- Keep it close to square. If the image is more than twice as wide as it is tall, or the other way round, the tool warns that it will shrink to a thin strip and suggests Crop to square.
- Trim empty margins. Transparent space around the artwork counts as part of the image, so a logo with wide margins comes out smaller in the tab. Crop it tightly in your image editor first.
- Don't worry about resolution for the ICO. Its largest image is 48 px, so most logos have plenty of detail. The notice about images under 512 px only concerns the larger home-screen icons in the package.
Check the 16 px, enlarged preview. It shows the tab-size icon four times bigger, pixel by pixel, so you can see whether thin lines and small gaps survive.
favicon.ico only, or the full package?
Both downloads use the same ICO. Which one you want depends on what you're setting up:
| You need | Download |
|---|---|
| A single ICO file, because that's what your site or app asks for | favicon.ico only |
| Tab icons for every screen, with PNG copies at 16 and 32 px | Download favicon package |
| An icon for when someone adds your site to an iPhone or Android home screen | Download favicon package (apple-touch-icon.png, icon-192.png and icon-512.png) |
| A web manifest and the HTML lines to paste into your page's head | Download favicon package |
The package is a ZIP with favicon.ico, the PNG icons, site.webmanifest and a README with the HTML to paste. If you start from an SVG, the SVG is included too. The HTML is also shown on the page with a Copy button. For installing it on your site, see the Favicon Generator.
Desktop icons and older software
This converter is made for website icons. If you want an icon for a desktop shortcut, a folder or an app, its ICO may not be the right file: it stops at 48 px, so larger icon views would have to enlarge it. The images inside are PNG-encoded, which current browsers and many modern programs read, but some very old desktop software only accepts the older BMP-style ICO, which this tool doesn't create.
Whatever you use it for, your image stays on your device. It's decoded, resized and packed into the ICO by your browser, and nothing is sent to UploadWell.