DVD and Optical Disc Storage

The DVD, or Digital Versatile Disc, is an optical storage medium that uses a laser to read and write data on a spinning disc. It shares the 120 mm size of the compact disc but stores far more, because it uses a shorter-wavelength red laser and finer track spacing. This higher density made the DVD suitable for full-length movies, software and general data storage, with a single-layer disc holding several gigabytes and dual-layer discs holding more.

DVDs come in pressed read-only form for commercial movies and software, and in writable forms for home recording. Recordable discs (DVD-R and DVD+R) can be written once, while rewritable discs (DVD-RW, DVD+RW and DVD-RAM) can be erased and recorded many times. The two competing “dash” and “plus” families were developed by different industry groups; most modern drives handle both. Writable discs store data by using a laser to alter a recording layer, either a dye or a phase-change material whose reflectivity changes between recorded and blank states.

The DVD followed the CD and was in turn followed by higher-capacity optical formats. The Blu-ray Disc, which uses a blue-violet laser of shorter wavelength, packs data more tightly still and was designed for high-definition video and larger data volumes. Although downloads and streaming have reduced the role of optical media, DVDs and related discs remain in use for video distribution, software, backup and archiving.

Frequently asked questions

What is the difference between DVD-R and DVD-RW?

A DVD-R can be written only once, while a DVD-RW is rewritable and can be erased and recorded many times. The plus family, DVD+R and DVD+RW, works similarly with a different recording standard.

How does a DVD store more than a CD?

It uses a shorter-wavelength red laser and more closely spaced tracks, packing data more densely so a single disc holds several gigabytes rather than a CD's smaller capacity.

How does Blu-ray differ from DVD?

Blu-ray uses a blue-violet laser with a shorter wavelength, allowing denser recording and much larger capacity, which suits high-definition video and big data files.