A Blu-ray Disc (BD) is a high-capacity optical disc storage medium designed for the storage and distribution of high-definition video, audio, and large volumes of digital data. It is read using a 405-nanometre blue-violet laser, which has a shorter wavelength than the red laser used by DVDs, allowing the laser to focus more precisely and read much smaller pits and narrower track spacing. This enables significantly higher storage density and data transfer rates.
A standard single-layer Blu-ray Disc stores 25 GB of data, while dual-layer Blu-ray Discs store 50 GB. Extended formats such as BD-XL increase capacity to 100 GB (triple-layer) and 128 GB (quad-layer), primarily for archival, professional, and data-centric use. Blu-ray formats include BD-ROM (read-only, used for commercial films and games), BD-R (recordable), and BD-RE (rewritable).
Blu-ray Discs are commonly used for high-definition and Ultra HD (4K) movie distribution, console gaming, large software delivery, and long-term data archiving due to their capacity and durability. While streaming services and solid-state storage have reduced consumer reliance on physical media, Blu-ray remains important where high bit-rate video quality, offline access, and permanent physical storage are required.