LRX files are only read by the Sony e-reader products such as the Sony Portable Reader and the Sony Librie. However, the LRX files for the Librie are not compatible for the Portable Reader, since the DRM is not the same. In addition, the LRX file extension is not compatible with other e-readers such as the Amazon Kindle, the Barnes and Noble Nook or the Mobipocket reader.
Digital rights management technology is a form of protection for easily transferable and readable files. DRM is not just applied to LRX files; it is used to copyright all kinds of digital media files, from videos to podcasts to MP3 music files. DRM technology encrypts the LRF file, preserving its file format and preventing the file from becoming converted to another file format. By using DRM to create LRX files, Sony ensures its e-books can only by read by its own devices. LRF and LRS files can be converted into other formats, but the DRM extension encrypts the LRX file and prevents it from being converted to other e-book formats.
The e-books with an LRX DRM encryption are binary book files. Binary book files are created from an XML-based source file, so they are specifically coded and similar to an XML program. Other e-book file formats use other formats to encode the e-book text, like regular HTML, XHTML or PDF file formats. A binary book file uses binary coding to create it. The LRF file is a binary book file without DRM, and then it becomes the LRX file extension as a binary book file with DRM.
The Sony Reader Library is e-book computer software used in conjunction with the Sony Portable Reader to import and transfer files to the device. The Reader Library can also be used as a desktop e-reader to read LRX files directly on PC and Mac OS X computers. It can also read other file formats, including LRS and ePub. Sony is the only company to use the LRX file extension with its e-books. However, as of August 2009 Sony is discontinuing its BBeB format and moving to ePub.