ICO & ICNS Icon Converter

About the ICO & ICNS Icon Converter

Turn a logo or picture into a real multi-size icon: a Windows .ico with every size you tick (16 to 256 px, the 256 px image PNG-compressed as Windows expects) and a macOS .icns with the ten images of an Apple iconset (16 to 512 px, each also at @2x for Retina screens). Every size is drawn separately from your original — SVG drawings are rendered sharp at each size — and small sizes can be sharpened so they do not turn to mush. You see each size at its real pixel size, on a light, dark or transparent background, before you download.

Going the other way, drop any .ico, .cur, .ani or .icns file to see every image stored inside — sizes, bit depth, cursor hotspots, the frames of animated cursors and the dark-mode set of Mac icons — and save them as PNG, one by one or all in a ZIP. Everything happens in your browser; nothing is uploaded.

Common uses

• Giving a Windows desktop program, shortcut or installer its .ico file.
• Building the .icns for a macOS app, a DMG volume or a document type.
• Making a favicon.ico with 16, 32 and 48 px from an SVG logo.
• Getting the high-resolution PNG out of an .ico or .icns you only have as an icon.
• Checking which sizes and colour depths an icon or cursor really contains.

What goes into the .ico

An ICO file is a directory of images, each with its own size, following the layout in Microsoft’s Icons article. Sizes below 256 px are stored as 32-bit bitmaps with an alpha channel and an AND mask that marks the transparent pixels (for programs that ignore alpha); the 256 px image is stored as a PNG, which is how Windows Vista and later keep large icons small. Tick Store every size as PNG for an even smaller file if you only target current Windows.

Microsoft’s app icon guidance asks for at least 16, 24, 32, 48 and 256 px; All Windows sizes adds the in-between sizes Windows uses at 125–400 % display scaling (20, 30, 36, 40, 60, 64, 72, 80 and 96 px), so Windows rarely has to scale your icon.

What goes into the .icns

The .icns holds the images of an Apple iconset — 16, 32, 128, 256 and 512 px, each also at double size — as PNG, plus the classic 24-bit colour and 8-bit mask pairs (is32/s8mk and il32/l8mk) for 16 and 32 px, which every macOS version draws. The .iconset (ZIP) button gives the same images as icon_16x16.png … icon_512x512@2x.png, the folder that Xcode and iconutil -c icns expect. Apple’s Human Interface Guidelines design app icons at 1024 × 1024 px, so start from that size for the sharpest Mac icon.

Sharp small sizes

Each size is made straight from your original, never from another size. Pictures are shrunk by averaging exactly the pixels each icon pixel covers, with transparency taken into account so edges do not get dark fringes; enlarging uses a cubic filter, or hard square pixels with Pixel art. Because shrinking a detailed picture to 16 px softens it, Sharpen small sizes adds a light unsharp mask at 48 px and below (strongest at 16–24 px). For a logo that must read at 16 × 16 px, a simplified version of it often works better than any filter — check the 16 px tile on both backgrounds.

Reading icon files

• ICO and CUR: PNG images are saved exactly as stored; bitmaps of 1, 4, 8, 16, 24 and 32 bits per pixel are decoded with their AND masks. Cursor hotspots are shown.
• ANI (animated cursors): every frame, with the frame timing.
• ICNS: PNG, ARGB, 24-bit RGB with masks, and the old 1-, 4- and 8-bit images with Apple’s standard palettes, including the dark-mode, selected and template sets inside newer icons.

Limitations

• Icons up to 256 px (ICO) and 1024 px (ICNS); files up to 100 MB.
• ICNS images stored as JPEG 2000 (used by some older Mac icons) are listed but cannot be decoded, because browsers have no JPEG 2000 decoder.
• Cursor pixels that invert the screen colour (a Windows effect) cannot be stored in PNG; they come out transparent.
• Making cursors (.cur with a hotspot) and icons inside .exe or .dll files is not supported.
• Colours are taken as sRGB; colour profiles in the source picture are applied by the browser when it opens it.

Privacy

Everything happens in your browser. What you enter or open here is not uploaded or stored by MySmartCoPilot.