Image to ICO — Free, Fast & Private
An .ico file is a small bundle: an index, then several complete pictures of the same artwork at different square sizes. So the question is which family of sizes to embed, not which codec. The tool above takes a PNG, JPEG or WebP, renders each size you tick and packs them into one downloadable file. It all runs in this tab, and the artwork never leaves your device.
Why two programs show different pixels from one file
Nothing in the format says which entry a reader must use. A browser tab on an ordinary display takes the 16px entry, and on a high-density screen the same slot takes the 32px one. Windows asks by view: small icons 16, medium 32, large 48, extra-large 256. At display scalings in between, the shell grabs the nearest larger entry and shrinks it, which is why icons look soft when a size is missing.
Which resolutions belong in the bundle
All of 16, 32, 48 and 256 are on by default. For a website favicon, 16, 32 and 48 are the sensible set, and 256 is extra weight every visitor downloads. For a Windows application, shortcut or folder, keep all four so the shell does not have to improvise. Each size is rendered separately from your original rather than chained off the previous one, so the small entries are as sharp as the source allows.
What your source image needs
PNG and WebP carry an alpha channel through to the icon. A JPEG has none, so its background becomes a solid backdrop in every entry; to avoid a white box around a logo, remove the background first. A non-square source is centred on a transparent square, not cropped or stretched. At 16 pixels square there is very little room, so hairline strokes, gradients and text turn to mush; convert a simplified mark for the small sizes.
Where the icon goes
For a website, put it at the domain root as favicon.ico. A Windows shortcut uses Properties, then Change Icon. For the Apple home-screen icon, the manifest icons and the markup that declares them, the favicon generator produces the whole set. If your source is an unoptimised export, the PNG compressor is worth running for the copy you keep.
Image to ICO results on real files, measured
| File | Before | Inside the .ico | Corner pixel | .ico total |
|---|---|---|---|---|
| 12 MP phone photo | JPG · 4032 × 3024 px · 3.73 MB | 4 PNG entries16 px · 745 B32 px · 2.37 KB48 px · 4.88 KB256 px · 123.5 KB | Transparent | 131.6 KB |
| Portrait / headshot | JPG · 3264 × 4653 px · 2.25 MB | 4 PNG entries16 px · 678 B32 px · 1.97 KB48 px · 3.97 KB256 px · 84.7 KB | Transparent | 91.4 KB |
| Screenshot (PNG) | PNG · 1280 × 800 px · 88.1 KB | 4 PNG entries16 px · 336 B32 px · 714 B48 px · 1.27 KB256 px · 9.22 KB | Transparent | 11.6 KB |
Measured 2026-10-07 in Chromium 145.0.7632.6 by converting each file with this page’s tool at its default sizes and parsing the .ico it downloaded: how many entries are inside, how each one is stored, and its bytes. The photos and scans are CC0 or public-domain files from Wikimedia Commons; the screenshot is MiniPx's own. Sizes are shown as the tool shows them (1 KB = 1,024 bytes).