Once upon a time in Hexadecimal

6F 6E 63 65 20 75 70 6F 6E 20 61 20 74 69 6D 65

Character Breakdown

Char	Hex	Decimal
o	0x6F	111
n	0x6E	110
c	0x63	99
e	0x65	101
	0x20	32
u	0x75	117
p	0x70	112
o	0x6F	111
n	0x6E	110
	0x20	32
a	0x61	97
	0x20	32
t	0x74	116
i	0x69	105
m	0x6D	109
e	0x65	101

Once upon a time in Other Codes

Once upon a time in Morse Code Once upon a time in Binary Once upon a time in Braille Once upon a time in NATO Alphabet