ET is a document format: it stores data in the ET format. FB2 is a ebook format 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. Converting between these two formats is common when the source application does not support FB2 natively or when the target platform only accepts FB2. 1converter processes this conversion server-side using open-source tools. Files are transferred over HTTPS, converted on secure cloud servers, and automatically deleted after 24 hours.