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Byte Order / Endianness
All values in the Universal Binary Specification (UBJSON) 2.0 are stored in little-endian byte order. Among other significant, breaking changes, this is another made on the journey to the 2.0 respecification.
The reason for this change is that while flipping byte order is near-free in modern hardware, the dominance of little-endian hardware (x86 and ARM) in the personal, professional and server space has made this a no-brainer.
This is also inline with the paths modern binary file formats like FlatBuffers have taken as well.