Blu-ray Disc
Optical format that succeeded DVD. Sony-led, launched 2003. Uses blue-violet laser (405 nm) for higher storage density. Won the format war against Toshiba's HD DVD in 2008.
Single-layer 25 GB, dual 50, BD-XL 100/128. 4K UHD Blu-ray (2016) supports HDR + Dolby Atmos. PlayStation 3 + 4 + 5 played a key role in adoption. Streaming (Netflix, Amazon Prime) made the format historical — physical discs are a nostalgia market now. Sony stopped manufacturing recordable Blu-ray discs in 2024. Film collectors still argue that 4K UHD discs give better quality than streaming (compression-fewer).