The XLS file format stores data in the XLS format. Converting to EPUB produces a ebook file that packages HTML, CSS, and images in a zipped OPS container as an ISO-standardised ebook format that reflows text to fit any screen width. 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 EPUB 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.