The HTML file format stores data in the HTML format. Converting to FB2 produces a ebook file that stores data in the FB2 format. This reformats the fixed-layout document into a reflowable ebook that adapts to screen size. Metadata such as creation date and embedded colour profiles is preserved where the target format supports it. This makes FB2 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.