Text to hex

Type on the left and two hex digits appear for each byte. Separator puts a space between bytes, a comma, or nothing at all, which is the form you want when pasting into code.

Swap the boxes to go the other way. The hex to text page starts in the decode direction if that's the job you arrived with.

A byte holds a number from 0 to 255. In hex that's 00 to FF, and it's never more or fewer than two digits. Four binary digits map onto exactly one hex digit, so eight map onto exactly two, with nothing left over.

Decimal has no such luck. A byte is one, two or three decimal digits depending on its value, so a run of decimal numbers needs separators to stay readable. Hex doesn't. 48692063616665 can be split into pairs by anyone, and that's why every hex dump, colour code and MAC address is written this way.

Accents and emoji cost more than one byte here too, on the same UTF-8 rules as binary. The é in the sample is c3 a9.

Base 16 needed a name in the early 1960s and the obvious one was already in use. Writers had called it sexadecimal, built the ordinary way from the Latin for six and ten, and Bendix used that word in manuals into the 1960s.

IBM went with hexadecimal instead, mixing the Greek hexa with the Latin decim. It's a hybrid that classicists object to on principle, and the reason for it is generally understood to have been the first syllable of the alternative. The word arrived with the System/360 documentation and never budged.

The letters had competition too. Early machines used u through z, or k through p, for the digits past 9. A B C D E F won because it needed no new characters on a keypunch, and because sorting stayed sensible.

Text to binary shows the same bytes as bits, four times longer and easier to read one flag out of. Base64 packs three bytes into four characters, so it's denser than hex and unreadable by eye.

For the number behind a character rather than the bytes it's stored as, use the Unicode converter.