Digital ebook saved in the EPUB format, an open XML-based format for digital books and publications; provides a standard digital publication format for publishers and consumers; can be viewed with supporting software programs and hardware devices, such as the Sony Reader and Barnes & Noble Nook.
The EPUB format is based on three open standards, which are all maintained by the International Digital Publishing Forum (IDPF).
- The Open Publication Structure (OPS), which defines the content markup
- The Open Packaging Format (OPF), which describes the ebook structure
- The Open Container Format (OCF), which packages all the ebook files together in a compressed format
NOTE: Many commercial ebooks include digital rights management (DRM) protection. These files can only be opened on devices that have been authorized to view the ebook.