WordNet (r) 3.0 (2006):

yottabyte
    n 1: a unit of information equal to 1000 zettabytes or 10^24
         bytes [syn: yottabyte, YB]
    2: a unit of information equal to 1024 zebibytes or 2^80 bytes
       [syn: yottabyte, yobibyte, YB, YiB]

The Free On-line Dictionary of Computing (30 December 2018):

yottabyte

    (YB) A unit of data equal to 10^24 bytes but see
   binary prefix for other definitions.  A yottabyte is 1000^8
   bytes or 1000 zettabytes.

   It is estimated that the web contains about one yottabyte of
   data (2013).

   1000 yottabytes has been called one brontobyte.

   See prefix.

   (2013-11-04)