Abbreviation for High Density Digital Versatile Disc. A digital optical media format that is being developed as a standard for high-definition DVD. HD DVD is similar to the competing Blu-ray Disc, which also uses the same CD-sized optical media and 405nm-wavelength blue laser. HD DVD is promoted by Toshiba, NEC, Sanyo, Microsoft, and Intel, and is backed by New Line Cinema, Paramount Pictures, Universal Studios, and Warner Bros.

HD DVD has a single-layer capacity of 15GB and a dual-layer capacity of 30GB. Toshiba has announced a triple-layer disc is in development, which would offer 45GB of storage. This is smaller than the competing Blu-ray disc, which supports 25GB for one layer and 50GB for two, but HD DVD proponents point out that multi-layer Blu-ray discs are still in development. The surface layer of an HD DVD disc is 0.6 mm thick, the same as DVD but thicker than the Blu-ray Disc’s 0.1 mm layer. HD DVD media promises to cost less to manufacture than Blu-ray, as HD DVD only requires modification of existing DVD disc production lines. Both formats will be backward compatible with DVDs and both employ MPEG-2 as their primary video compression techniques.

One advantage HD DVD has is its support by the DVD Forum, a group of hardware and media manufacturers that sets specifications and standards for DVD-based content. Blu-ray was developed outside of the DVD Forum, and was never submitted to the forum for consideration.

In April 2005, Apple Computer, a member of the DVD Forum, updated DVD Studio Pro to support authoring HD content. DVD Studio Pro allows for the burning of HD DVD content to DVDs, and HD DVD media will be supported as burners become available.