The exabyte (derived from the SI prefix exa-) is a unit of information or computer storage equal to one quintillion bytes (short scale). The unit symbol for the exabyte is EB. The unit prefix exa indicates the sixth power of 1000:

The exbibyte, using a binary prefix, is the analogous power of 1024 bytes.

In principle, the 64-bit microprocessors found in many computers can address 16 exbibytes, or just over 18 exabytes, of memory.

Several filesystems use disk formats that support theoretical volume sizes of several exabytes, including Btrfs, XFS, ZFS, exFAT, NTFS, HFS Plus, and ReFS.

A popular expression claims that "all words ever spoken by human beings" could be stored in approximately 5 exabytes of data, often citing a project at the UC Berkeley School of Information in support. The 2003 University of California Berkeley report credits the estimate to the website of Caltech researcher Roy Williams, where the statement can be found as early as May 1999. This statement has been criticized.Mark Liberman calculated the storage requirements for all human speech at 42 zettabytes (42,000 exabytes, and 8,400 times the original estimate), if digitized as 16 kHz 16-bit audio, although he did freely confess that "maybe the authors [of the exabyte estimate] were thinking about text."