yottabyte

Yottabyte (symbol YB) is a unit of digital information equal to 10^24 bytes. It is the largest SI prefix commonly used to express data storage. In decimal terms, 1 YB equals 1,000,000,000,000,000,000,000,000 bytes. It is equal to about one billion petabytes or one million exabytes.

In binary terms, the closest standard is the yobibyte (YiB), defined as 2^80 bytes. One YiB is about 1.2089×10^24 bytes, so 1 YB is about 0.827 YiB.

The prefix “yotta-” is derived from the Greek oktō, meaning eight, and was adopted for the SI system in 1991; the symbol is Y.

In practical use, yottabytes are discussed mainly in the context of future-scale data storage and global-scale data centers. As of the early 2020s, no consumer or enterprise storage system has reached 1 YB, and yottabyte-scale storage remains largely in planning, theoretical, or aspirational discussions rather than everyday deployment.