CDsDVDsBluray

CDs, DVDs, and Blu-ray discs are optical storage media used to store digital data, video, and audio. They encode data as microscopic pits and lands on a polycarbonate substrate, read by a laser in a player or drive. Each format uses a different laser wavelength and storage density, which affects capacity and compatibility. CDs originated in the 1980s for consumer audio and later supported data storage; DVDs emerged in the 1990s to provide higher capacity for movies and software. Blu-ray, introduced in the mid-2000s, further increased density to support high-definition video and large data sets.

Capacities and common variants. A standard CD holds about 700 MB of data or 74–80 minutes of audio. DVD capacities are about 4.7 GB for a single-layer disc and 8.5 GB for dual-layer discs. Blu-ray discs typically store 25 GB on a single-layer disc and 50 GB on dual-layer discs; the format has higher-capacity variants under the BD-XL designation, up to 100 GB or 128 GB with additional layers. Common formats include CD-ROM, CD-R, CD-RW; DVD-ROM, DVD-R, DVD+R, DVD-RW, DVD+RW; BD-ROM, BD-R, BD-RE.

Uses and distribution. CDs are widely used for music and software distribution; DVDs for movies, television, and data backups; Blu-ray for high-definition video, 3D content, and large data archives. Blu-ray is also used for 4K Ultra HD content on newer media and players. Some discs include additional features such as BD-J interactive content.

Durability and current status. Optical discs are susceptible to scratches, surface damage, and environmental factors, and archival longevity varies by disc type and storage conditions. Following the rise of streaming and solid-state media, optical discs have declined in consumer importance but remain in use for physical media distribution, gaming, and archival storage, aided by improvements in protective coatings and information longevity technologies.