ICO is the icon format used for favicons and Windows icons. One ICO file can hold several sizes of the same picture, from 16 by 16 pixels up to 256 by 256. Converting ICO to PNG gives you an exact, lossless copy that keeps transparency.
PNG is lossless, so every pixel is kept exactly, and it supports transparency. That makes it the safe choice for screenshots, logos and graphics. PNG files are larger than JPG or WebP for photographs, so use it when exactness or transparency matters more than size. Converting an ICO gives you one regular image, taken from the icon, usually its largest size. Icons are small, so the result is small too, and enlarging it will look soft.
PNG is lossless, so there is no quality setting. The pixels are kept as they are. The pixel dimensions follow the original, each file keeps its name with only the extension swapped, and no metadata or watermark is added. Everything runs in your browser, so your images are never uploaded.
Tip: To get a usable picture of a favicon or app icon, PNG is the best choice because it keeps the transparency and every pixel exactly.
Not with PNG. It is lossless, so the pixels are kept exactly as they are.
Icons usually have transparent corners or backgrounds. PNG and WebP keep them. JPG cannot, so transparent areas become white.
The image is read by your browser, which normally gives the largest size stored in the file.
Yes. Add them all, convert once and download a single ZIP. Only the extension changes. A file named favicon.ico becomes favicon.png.
No. The conversion happens in your browser and the files never leave your device.