What is hexadecimal?
Hexadecimal (hex) is base 16: it counts with the digits 0–9 and the letters a–f.
One byte, a number from 0 to 255, is always exactly two hex digits, from 00 to ff.
That's why hex is the usual way to show raw bytes: in hash values, colour codes, memory dumps, network
packets and escape sequences.
How the conversion works
Text is first turned into UTF-8 bytes, then each byte is written as two hex digits. Plain English letters
take one byte each, so Hi becomes 4869. Other characters take two to four bytes:
€ becomes e282ac.
Going the other way, the hex is turned back into bytes and read as UTF-8. You can paste hex in common
formats such as 48 69, 48:69 or 0x48 0x69. If the bytes aren't valid
UTF-8 text, you'll see a warning and the bad bytes are shown as �.