A DVD+RW is a rewritable optical disc with equal storage capacity to a DVD+R, typically 4.7 GB (interpreted as ˜ 4.7 · 109, actually 2295104 sectors of 2048 bytes each). The format was developed by a coalition of corporations, known as the DVD+RW Alliance, in late 1997, although the standard was abandoned until 2001, when it was heavily revised and the capacity increased from 2.8 GB to 4.7 GB. Credit for developing the standard is often attributed unilaterally to Philips, one of the members of the DVD+RW Alliance. Although DVD+RW has not been approved by the DVD Forum, which produced a competing standard, the format is too popular for manufacturers to ignore, and as such, DVD+RW discs are playable in three quarters of today's DVD players.

DVD-RW is a direct competitor with DVD+RW. Hybrid drives that can handle both, often labeled 'DVD±RW', are very popular as there is no single standard for recordable DVDs.

The rewritable DVD+RW was formalized as a standard earlier than its non-rewritable sister standard DVD+R, whereas the DVD Forum's analogous DVD-RW format was released later than its counterpart DVD-R was.

DVD+RW discs can be rewritten about 1,000 times, making them comparable with the CD-RW standard. DVD+RW discs are commonly used for volatile data, such as backups or collections of files. However, they are not as widely used for home DVD video recorders as DVD-RW, primarily because they were originally designed for storage of data, rather than of video. Of late, a number of cheaper and 'no-name' manufacturers have started releasing DVD recorders using the DVD+RW format rather than DVD-RW, leaving the branded manufacturers (except Philips, which helped to develop DVD+RW in the first place) to fly the DVD-RW flag. For computer use, the DVD-R or DVD+R non-rewritable disc types are vastly more popular than the rewritable DVD+RW or DVD-RW, and mail order or bulk pricing of non-rewritable media is significantly cheaper than their rewritable counterparts.

The recording layer in DVD-RW and DVD+RW is not an organic dye, but a special phase change metal alloy, often GeSbTe. The alloy can be switched back and forth between a crystalline phase and an amorphous phase, changing the reflectivity, depending on the power of the laser beam. Data can thus be written, erased and re-written.

DVD+RW supports random write access, which means that data can be added and removed without erasing the whole disc and starting over. This means that DVD+RWs can almost be treated like removable hard disks. Conversely, DVD-RW is more like CD-RW: to change data, one must erase the whole disc and start over again.

Wikipedia information about DVD+RW. This article is licensed under the GNU Free Documentation License . It uses material from the Wikipedia article 'DVD+RW'