The FB2 file format stores data in the FB2 format. Converting to ICO produces a image file that bundles multiple raster images at different resolutions (16x16 through 256x256) into a single file for use as application icons. This conversion changes the file's encoding, compression method, and supported feature set. Metadata such as creation date and embedded colour profiles is preserved where the target format supports it. This makes ICO the practical choice when the destination system requires it or when the original format is not supported by the target application. 1converter runs this conversion on the server: your file is uploaded encrypted over HTTPS, converted using trusted open-source libraries, and the output is held for 24 hours before automatic deletion.