ICO to PNG

An .ico file is not one picture but a small container holding the same icon several times: different pixel sizes for different places in Windows and browsers, and sometimes different color depths for very old displays. Extracting them gives you each version as a normal transparent PNG you can reuse in documentation, a design system or a new app.

What is inside an icon

The file starts with a directory listing every image: its width, height, color depth and where its data starts. Modern icons store each image as a complete PNG, which is compact and supports smooth transparency. Older icons, and the small sizes of many current ones, store a Windows bitmap followed by a 1-bit mask that marks transparent pixels. A typical favicon contains 16, 32 and 48 pixel sizes; Windows application icons add 24, 64 and 256.

How the extraction works

The tool reads the directory itself, so it does not depend on the browser understanding icons. PNG entries are decoded by the browser; bitmap entries go through a decoder written for this site that handles 1, 4, 8, 24 and 32 bits per pixel and applies the transparency mask. Every entry becomes a PNG named after the icon and its size, sorted from largest to smallest. With “Save every icon size” switched off, you get only the largest.

Choosing the right size

For reuse, start from the largest entry, usually 256 × 256 in Windows icons. If the largest is only 32 or 48 pixels, which is common for favicons, enlarging it will look soft; in that case look for the original logo on the website or ask its owner for a vector version. Designers sometimes hand-draw the 16 and 32 pixel versions with simplified shapes; those are useful as they are for small UI elements but not as a source for big graphics.

Color depth duplicates

You may find two or three images with the same size, for example 32 × 32 at 4-bit, 8-bit and 32-bit. They come from the time of 16-color and 256-color screens. The 32-bit version has a full alpha channel with smooth edges; the others have hard, staircase edges. Keep the 32-bit one unless you need the retro look.

Turning PNGs back into an icon

After editing, you can rebuild an icon from a PNG with PNG to ICO, or create a complete favicon set with the Favicon Generator. For a JPG copy on a solid background, for documents that do not accept PNG, use ICO to JPG.

When a file will not open

A file with an .ico extension that is actually a PNG or a JPG is recognised from its content and converted anyway. Damaged icons, where the directory points past the end of the file, give an error instead of broken images. Cursor files (.cur) share the ICO structure and usually extract fine too.

Practical uses for extracted icons

Writers documenting software need clean pictures of toolbar and application icons. Developers migrating an old Windows program to the web need its icons as PNG sprites. Designers auditing a brand check whether every favicon size was actually produced from the current logo. Security analysts compare the icons of suspicious executables extracted with other tools. In each case, having every size as a separate, correctly transparent PNG saves the tedious work of screenshotting and cutting out icons by hand.