Zone Bit Recording (ZBR) is used by disk drives to store more sectors per track on outer tracks than on inner tracks. It is also called Zone Constant Angular Velocity (Zone CAV or Z-CAV or ZCAV).

On a disk consisting of concentric tracks, the physical track length increases with distance from the center hub. Therefore, holding storage density constant, the track storage capacity likewise increases with distance from the center.

To implement ZBR, a drive's controller varies the rate at which it reads and writes - faster on outer tracks. Alternatively, the disk rotation rate could be slowed, as was done by the original Apple Macintosh floppy disk.

Products that use ZBR/ZCAV

• Commodore 1541 floppy disk
• Apple Macintosh 400K/800K floppy disk
• DVD-RAM
• HD-DVD-RW (note: not HD-DVD-ROM or HD-DVD-R)
• Most hard drives since the 1990s