Derivative Formats
The ubiquity of reading devices — from mobile phones, to tablets, to electronic paper — was predicted by Project Gutenberg. Rather than creating separate master files for each native format for the devices, automatic conversion is applied to one of the master formats. For years, Java-format eBooks were automatically created, and these were usable on many mobile phones.
Today, EPUB and MOBI (also known as Kindle) formats are the most common. Free software for conversion, called ebookmaker (previously called epubmaker) is used to create derivative formats. This helps to assure compatibility for different reader devices.