CD-RW or Compact Disc, Re writable is a CD format that allows repeated storing up of data on a disc, unlike CD-R disks on which one can only store up data once. The CD-RW format was brought together by Helwartt-Parkard, Ricoh, Mitsubishi, Philip, and Sony, in a 1997 supplement to Philip and Sony’s Orange Book. CD-RW is Orange Book 3(CD-MO was1 while CD-R was 2).

Prior to the introduction of the Orange Book, CDs had been read-only audio (CD-Digital Audio, illustrated in the Red Book), to be played in CD players, and CD-ROM to be used on computers’ CD-ROM drives. After the Orange Book, any computer user with a CD Recorder drive could produce their own CDs from their desktop computers. CD-RW drives can program both CD-R and CD-RW discs and can read any type of CD.

CD-RW discs need to be formatted before reuse. Different formatting method can be used, such as, “full” formatting in which the entirety of the disc is deleted, and “quick” formatting in which only meta-data areas (PMA, TOC and pregap, comprising a few percent of the disc) is cleared.

Quick formatting is far faster and is normally sufficient to allow rewriting the disc. Full formatting removes traces of the former data, often for confidentiality. It may be possible to recover data from full-formatted CD-RWs with special data recovery equipment. However, this is not commonly used except by government agencies due to its cost.

Although it may be somewhat inconvenient to have to be erasing disc every time one wants to add new data or change files, the capability of a CD-RW to be reused make it a good choice for making frequent backups. However, since CD-RWs can be formatted, they do not hold up data reliably for as long as CD-Rs do. Therefore, CD-RWs are used for temporary short or mid-term backups while CD-Rs are used for long-term backups.