ICO to BMP Converter

This tool turns a ICO file into a BMP file. Drop an image onto the upload zone or click it to browse your device, and a preview appears once the file has been decoded. Alongside the convert button you'll find a single convert button, since BMP output needs no extra settings. Nothing leaves your device: the file is read locally, converted locally, and the download link points at data held only in this browser tab.

Under the hood, the source file is decoded onto an HTML canvas element using the browser's own image loader — ICO decoding relies on the browser's built-in icon loader, which reads the largest frame in the file. Those pixels then land on an HTML canvas, from which they are re-encoded as BMP. Because canvas has no built-in BMP writer, the pixel buffer is read with getImageData and packed by hand into a 24-bit BMP file header and row structure.

As with any browser-based converter there are limits worth knowing. On the input side, multi-frame icons are read using whichever frame the browser's decoder selects, which is not always the largest one, and support for ICO as an source varies by browser. On the output side, The BMP writer produces an uncompressed 24-bit file with no alpha channel, so transparency is flattened onto a white background and output files are noticeably large.