JSON says -
Beyond size, XML lacks an explicit mechanism for representing large binary data types such as image data (although binary data can be serialized in either case by applying a general-purpose binary-to-text encoding scheme such as one of the Base-64 variants). JSON can represent them using arrays of numbers (representing bytes, or larger integer units up to the precision of 52 bits including the sign bit), because it can exactly represent IEEE-754 64-bit doubles (as specified in the ECMAScript standard).
Regards,
Dan