Blu-ray Disc

Blu-ray Disc (BD) is an optical disc storage format developed by the Blu-ray Disc Association, a group of consumer electronics and computer companies, as a successor to the DVD. It was designed primarily to store high-definition video, but it also serves as a general-purpose medium for data and computer software. Discs share the familiar 120 mm diameter of CDs and DVDs, so they fit the same physical form factor while holding considerably more information.

The name refers to the blue-violet laser the format uses to read and write data. Its shorter wavelength, around 405 nanometres, focuses to a smaller spot than the red laser used by DVD, which lets the data tracks and pits be packed more tightly. This finer recording allows a far greater capacity: a single-layer disc holds roughly 25 gigabytes and a dual-layer disc about 50 gigabytes, several times what a DVD can store. Later variants added more layers and higher capacities for ultra-high-definition video.

Blu-ray comes in read-only pressed discs (BD-ROM) used for movies and software, write-once recordable discs (BD-R), and rewritable discs (BD-RE). Recorders and players for the format were marketed alongside high-definition televisions, and Blu-ray competed with the rival HD DVD format before that format was discontinued. Because of its capacity and durability, Blu-ray media has also been used for data archiving and backup.

Frequently asked questions

Why is it called Blu-ray?

It is named after the blue-violet laser used to read and write the disc. The shorter wavelength allows data to be stored more densely than on a DVD.

How much can a Blu-ray Disc hold?

A single-layer disc stores about 25 GB and a dual-layer disc about 50 GB, well above the roughly 4.7 GB of a single-layer DVD.

Can a DVD player read Blu-ray discs?

No. Blu-ray requires a blue-violet laser, so a standard DVD player cannot read it, although most Blu-ray players can still read DVDs and CDs.