Sony Portable Reader File (.lrf)

The LRF file extension, known as the "Sony Portable Reader File," is a proprietary format developed by Sony for its eBook readers, specifically the Sony Reader. This format is part of the Broad Band eBook (BBeB) family, which also includes LRS and LRX file types. LRF files are designed to store eBooks and other textual content in a compressed binary format. They encapsulate various elements such as text, images, formatting, and pagination data, making them suitable for displaying rich content on Sony's eBook readers. The structure of an LRF file includes a header, a specified number of objects, and an object index, all stored in Intel (LSB first) order. This format was particularly popular during the early days of eBook readers, providing a way to efficiently store and display digital books on portable devices.

The LRF format, however, has become obsolete since Sony transitioned to the more widely adopted EPUB format in 2010. Despite its obsolescence, LRF files can still be opened and converted using various software tools. These tools allow users to convert LRF files to other formats like EPUB or PDF, ensuring that the content remains accessible even if the original Sony Reader device is no longer in use. The LRF format's decline in popularity is attributed to the rise of more versatile and open formats like EPUB, which offer better compatibility across different devices and platforms. Nonetheless, the LRF format played a significant role in the evolution of digital reading, marking an important chapter in the history of eBooks and portable reading devices.