NSData Class Reference (emphasis added)

Overview

NSData and its mutable subclass NSMutableData provide data objects, object-oriented wrappers for byte buffers. Data objects let simple allocated buffers (that is, data with no embedded pointers) take on the behavior of Foundation objects.

The size of the data is subject to a theoretical limit of about 8 ExaBytes (in practice, the limit should not be a factor).

[ exa = 10¹⁸ ]