PNG to Windows App Icon (multi-size .ico)
Windows .exe installers, custom desktop shortcuts, and application icons all want the same thing: a single .ico file containing every size Windows might draw at, from 16×16 in the title bar up to 256×256 in the Explorer thumbnail grid. Drop a square PNG below and download one .ico with the full ladder packed inside.
The conversion runs entirely in this tab. The PNG never leaves your computer.
What’s in the output
One .ico file containing 16, 24, 32, 48, 64, 128, and 256 pixel square images. Windows picks the right one at each render point:
16 and 24 cover the title bar, taskbar small mode, and Explorer details view. 32 is the standard desktop and Start tile. 48 is the Explorer medium icons mode. 64 and 128 cover the Explorer large and extra-large modes plus high-DPI scaling. 256 is what Vista and later use for the thumbnail view that appears when you hover over a file in folder previews.
Skipping any of those means Windows resamples a different size to fill the gap, which on small displays produces a fuzzy icon. The full ladder is about 100-150 KB depending on the source artwork. That is the right trade for a file that ships inside an installer or shortcut you only generate once.
Source PNG requirements
Start with a square PNG, ideally 256×256 or larger so the 256 slot does not have to be upscaled. Transparent background. Simple, high-contrast artwork (a logo or symbol, not a photograph) reads better at the 16×16 end of the ladder, where each pixel of detail matters a lot.
If your source is smaller than 256×256, the larger sizes in the .ico will be upscaled and look blurry. The converter does not refuse them, but the icon will not look great at thumbnail size.
Where to use the output
Drop the .ico file into the resource section of your installer (Inno Setup’s SetupIconFile=, NSIS’s !define MUI_ICON, WiX’s <Icon Id="..." SourceFile="...">), set it as the icon for a .exe via your build’s resource compiler, or right-click a Windows desktop shortcut, choose Properties, Change Icon, and point it at the file.
Just need a favicon?
A browser favicon does not need this many sizes. The standard favicon set (16, 32, 48) is under 10 KB and covers every place a browser will render an icon. If your goal is a website favicon, use favicon from PNG instead. The smaller .ico loads faster on every page request.
Common questions
Why not just use a single big PNG? Windows shell does not. The Explorer code that draws icons at 16×16 calls into a specific image lookup that wants a pre-rendered 16×16 entry. If only a 256×256 is available, Windows downsamples on the fly, producing a soft, fuzzy result that looks especially bad on title bars. Pre-rendering each size at the right resolution is the only way to get crisp results everywhere.
What about macOS .icns? Different format, different tool. .icns is for macOS application bundles. Windows app icons use .ico exclusively.
Can I add custom sizes? Not from this page. The full Windows ladder covers every practical render point; adding 512 or 1024 produces files that bloat the executable without any place Windows would actually use them. If you have a specific custom requirement, write in.
What is the ICO format?
ICO is a Windows container that packs multiple image entries into one file. Each entry has its own pixel dimensions and color depth, and the application using the icon picks whichever entry matches its current rendering size. The format predates Windows 95 but was extended to support PNG-compressed entries in Windows Vista, which is how the larger 256-pixel sizes fit into a reasonable file size today.