ICO to PNG Converter

Encoding: the ICO uses each size stored as a headerless BMP or as a complete PNG; PNG uses lossless DEFLATE with a prediction filter chosen per row, and the download is a lossless 8-bit PNG with full alpha.

Bit depth: 1 to 32 bits per pixel, set per size in the ICO; PNG allows 1, 2, 4, 8 or 16 bits per channel, and the PNG written here has 8 bits per channel.

Colour: RGB or a palette, per image in the ICO; PNG supports RGB, greyscale, or an indexed palette of up to 256 colours, written here as 8-bit sRGB.

Transparency: the ICO stores it as 8-bit alpha in 32-bit and PNG entries, or a 1-bit mask in old icons; the PNG keeps it as a full alpha channel, so edges and shadows can fade smoothly.

Other images: the ICO can hold several sizes of the same picture, typically 16, 32, 48 and 256 px; only the main image is converted.

Metadata: the ICO can carry only a directory of the sizes inside, with no EXIF; PNG can carry text chunks, an ICC profile, physical resolution and EXIF in an eXIf chunk, but nothing is copied across.

ICO is a container that bundles several sizes of the same icon (16, 32, 48, 256 px) into one file. It is still the most compatible format for website favicons and Windows app icons.

An ICO starts with a 6-byte ICONDIR (type 1 for icons) and a 16-byte entry per image giving width, height, colour count and offset. Each image is either a BMP without its file header plus an AND mask, or a complete PNG.

ICO files usually come from website favicons, Windows programs and installers.

PNG stores pixels losslessly with full alpha transparency. It is ideal for screenshots, logos, UI and anything with sharp edges, but photos saved as PNG are several times larger than JPEG.

A PNG opens with an 8-byte signature and is a chain of chunks, each with its own CRC: IHDR (size, depth, colour type), optional PLTE and tRNS for palettes, one or more IDAT chunks with the compressed rows, and IEND.

PNG is the better choice for screenshots, logos, graphics and anything that needs transparency, while ICO suits favicons and Windows icons.

PNG strengths: Lossless: no quality loss, ever; Full transparency with smooth edges; Perfect for text, screenshots and graphics. Drawbacks to weigh: Large files for photographs; No standard animation (that is APNG).