A dual layer Digital Versatile Disc (DVD) writer is a type of electronic entertainment device that can record data to a dual layer DVD, i.e., a recordable disc with two physical layers. The second layer allows the disc to hold almost twice as much data as a single layer DVD. There are competing formats for recordable dual layer DVDs, but most recent DVD writers and drives are compatible with all formats.
Although DVDs may all look the same to the naked eye, there are several different types. The most common standard, known as DVD5, has a single layer and single side. This kind of disc can hold up to 4.7 gigabytes worth of data. Another type, DVD9, is a single-sided dual layer disc that holds up to 8.54 gigabytes of data. DVD5 and DVD9 are used for both commercial discs produced by movie studios and recordable discs for home use.
Dual layer media to some extent resembles two single-layered DVDs squished together. A dual layer DVD contain two layers of data on the same side of the disc and separated by a semi-reflective metal layer. To write data to the second layer, a dual layer DVD writer must have a laser capable of shifting its focus past this semi-reflective metal. This requirement means that the earliest DVD writers lack the capability of recording to dual layer discs.
There are two main formats for recordable DVDs: DVD-R and DVD+R. Both types of disc come in single layer and double layer varieties. Some early DVD players and writers would only accept one type of format, but more recent consumer electronics devices, including DVD players, video game consoles, and Blu-ray disc players, support both formats. Almost every dual layer DVD writer also supports writing to DVD-R and DVD+R. Standards for dual layer rewritable DVDs (DVD-RW/DVD+RW) also exist, but these discs were never widely manufactured and can be difficult to find.
A dual layer DVD writer isn’t limited to dual layer discs, and most can write to many types of media. In addition to dual and single layer recordable DVDs, rewritable DVDs (DVD-RW or DVD+RW), and recordable or rewritable compact discs (CD-R and CD-RW) are often supported. Manufacturers often include slogans or marks with the words “multi” or “super” in them to indicate a dual layer DVD writer compatible with many different formats. Blu-ray disc writers will frequently support dual layer DVDs as well.