Is based on the XML format. Its main tasks are: precise display on a variety of devices, full preservation of document structure, ability to be transformed into other formats. Unlike other popular e-book formats, fb2 does not specify the appearance options for different devices’ displays. The format employs tools to indicate the different parts of the book – verses, epigraphs, quotations.

Format for representing colors in the three primary colors (red, green and blue), each of which has 255 gradations. In contrast to the standard RGB, it allows you to change the transparency of the entire image using the opacity parameter. It is less flexible in terms of transparency settings than RGBA.