What this tool exports
It makes square PNGs from one source image. The source is centre-cropped to a square, scaled to the target size, and shaped by one of three choices: square, circle, or rounded, which uses a corner radius of 22 percent of the icon size. Because iOS applies its own rounded mask to the App Store and touch icons, the 180 and 1024 px sizes are always exported square when you pick Rounded, so they do not get double-rounded. Circle applies to every size. You can add 0 to 30 percent padding, and optionally fill a background colour behind the picture. Without a background fill, areas outside a rounded or circle shape are transparent, and so is any transparency in your source.
The ten sizes it produces are fixed: 16, 32, 48, 64, 128, 180, 192, 256, 512 and 1024 pixels. Each downloads as yourfile-SIZExSIZE.png. "Download all sizes (ZIP)" bundles all ten PNGs into one yourfile-icons.zip, so there is no flurry of separate downloads.
"Download favicon.ico" writes a single multi-image favicon.ico holding the 16, 32, 48 and 256 px versions, and the same file is added to the ZIP. The file is built by hand: a 6-byte header, a 16-byte directory entry for each image, then the four PNG images stored as they are, so even the 256 px size stays a compressed PNG rather than a large raw bitmap. In the directory a width of 0 stands for 256. Browsers, Windows shortcuts and Explorer all read this PNG-in-ICO layout, but a few very old programs (before Windows Vista) expect bitmap data instead. Only these four sizes go in the .ico, because the format cannot hold anything larger than 256 px.
How those sizes map to real platforms
| Size | Use |
|---|---|
| 16, 32, 48 | Browser tab and desktop shortcut favicons |
| 180 | Apple touch icon for adding a site to the iPhone home screen |
| 192, 512 | Web app manifest icons for a PWA |
| 1024 | Master size for the App Store listing; also a good source for the Play Store, which asks for 512 |
| 64, 128, 256 | General-purpose sizes for desktop apps and docs |
It is not a full native icon-set exporter. A shipped iOS app needs many more sizes (for example 20, 29, 40, 60, 76 and 83.5 pt at 1x, 2x and 3x, packaged in an asset catalog), and Android launchers use density-specific files such as 48, 72, 96 and 144 px. Xcode and Android Studio can generate those from one 1024 px source, so export the 1024 here and feed it to them.
Worked example
A 600 by 400 logo is cropped to its central 400 by 400 square. At 15 percent padding and size 192, the padding is round(192 x 15 / 100) = 29 px on each side, so the artwork is drawn at 134 px inside the 192 px canvas. With the rounded shape the corner radius is 192 x 0.22 = 42.2 px (at 180 or 1024 px the same icon is exported square for iOS).
Mistakes to avoid
- Submitting a pre-rounded icon to the App Store. Apple applies its own mask and expects a plain square without transparency. The Rounded option leaves the 180 and 1024 px sizes square for that reason, but Circle does not, and a source with transparency still has transparent pixels. For store builds choose Square and turn on Fill background. Rounded and circle shapes suit web, PWA and favicon use.
- Android adaptive icons keep important content within the central safe zone (66 dp of a 108 dp canvas), so use 15 to 20 percent padding if your art touches the edges.
- Starting from a source under 512 px produces soft large sizes. Begin from 1024 px or an exported SVG to PNG render.
- No artwork yet? The favicon generator builds icons from a letter or emoji. For a round profile image, use Circle Crop.