Blu-ray is an optical media format designed to replace DVDs by providing higher storage capacity and the ability to play back high-definition video. Blu-ray discs are used for distributing HD films and television shows, as well as video games for the PlayStation 4 / 5 and Xbox One / Series X consoles. A Blu-ray disc is the same physical size as a CD or DVD (120 mm in diameter and 1.2 mm thick) but can store significantly more data — up to 100 GB on a triple-layer disc.

A standard Blu-ray disc contains HD (1080p) video compressed using the H.264 codec, which is more efficient than the MPEG-2 format used by DVD video. Like DVDs, Blu-ray discs can incorporate interactive menus, multiple language options, and bonus material. An enhanced version of the Blu-ray format, Ultra HD Blu-ray, supports 4K HDR video through a combination of high-capacity dual- and triple-layer discs and the more efficient H.265 video codec. Ultra HD Blu-ray requires a compatible Blu-ray player that supports the newer codec but is physically the same format.

The name "Blu-ray" comes from the blue-violet laser the Blu-ray drive uses to read data. Like other optical disc formats, Blu-ray discs contain data encoded as a series of pits and bumps in reflective material on the underside of the disc, read by a laser in the disc drive and decoded. Blu-ray discs can store data far more densely than CDs and DVDs by using a narrower laser with a shorter wavelength — 405 nm, compared to 650 nm for DVDs or 780 nm for CDs.

While streaming video services can deliver HD and 4K video over the internet without discs, Blu-ray and UHD Blu-ray discs often provide better image quality. A disc's video bitrate is typically far higher than what is provided by streaming video services, which allows the video to use less compression and contain fewer artifacts. While it's often more convenient to stream a movie than it is to find and insert a disc into a Blu-ray player, film buffs prefer the superior video they get from physical media like HD and UHD Blu-ray discs.

Updated December 6, 2023 by Brian P.

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