What is BDXL? It is the latest format from the Blu-ray Disc Association , meaning, Blu-ray disc, XL, or extra large. BDXL discs are primarily for commercial applications, although many devices are entering the domestic computer marketplace. There are 2 disc sizes of BDXL disc, 100GB, for re-writable discs, and 128GB for write once media, and, like normal Blu-ray, the file system is UDF (Universal Disc Format) 2.5/2.6, but a normal Blu-ray disc (BD) device will not read a BDXL disc. Using the shorter wavelength 405nm blue laser, like all Blu-ray discs, this media holds 5 times more, on average than conventional DVD's. Although, not compulsory, all BDXL devices are fully backwards compatible, right down to CD playback, only a BDXL machine can use BDXL discs.