ICO Converter

What makes a real ICO file unique?

Unlike formats like PNG or JPEG, which hold a single pixel grid, an ICO file is a wrapper designed for icon storage. It contains a look-up table directory pointing to multiple distinct images of different sizes. This means a single `.ico` file can store a 16x16 icon for small browser tabs, a 32x32 icon for bookmark lists, and a 128x128 or 256x256 icon for system shells.

When you select sizes like 16x16, 32x32, and 128x128 in our converter, we create distinct canvases, downscale your high-resolution original image onto them with high-quality smoothing, compress them into independent PNG blocks, and package them together in a binary stream. The resulting file is a genuine, multi-resolution `.ico` container compliant with standard Windows and web browser specs.

Why use a client-side ICO converter?

Normally, compiling multi-resolution icons requires specialized software or command-line utilities like ImageMagick. Online converters often require you to upload your files, which presents security issues if you are working on private business logos or brand assets.

Our tool runs 100% locally. By generating raw file bytes in the browser via JavaScript ArrayBuffers and compiled directories, we can build the ICO header, write directories pointing to exact offsets, and assemble the file without sending a single byte to an external server. It is extremely fast, private, and compatible with all modern systems.