Text to hex converter

Paste hex on the left and it's read back as UTF-8 text, two digits to a byte. The sample spells Hi there. Swap the boxes to turn text into hex.

Decoding is forgiving about formatting. It ignores spaces, commas, colons and dashes, and strips 0x and \x prefixes, so you can paste from a hex dump, a debugger or a Stack Overflow answer without cleaning it up first. Separator changes what sits between bytes on the way out, and Letters picks lower or upper case.

One byte holds a number from 0 to 255, which takes three digits in decimal and eight in binary. In base 16 it always takes exactly two, so a row of bytes lines up into neat columns and you can read a dump without counting.

The four bits behind each hex digit have their own name. A nibble, half a byte. The joke has been in the literature since the 1950s.

Hex uses A to F, so a handful of English words can be written as numbers. Programmers have been doing it for decades: 0xDEADBEEF marks freed memory in some systems, and 0xCAFEBABE is the first four bytes of every compiled Java class file, picked by James Gosling after a lunch spot his team called Cafe Dead.

It's worth learning a few. A file that begins 0xCAFEBABE or 0x89504E47 is telling you what it is before you open it, which is how the cipher identifier recognises formats too.

Hex, binary and Base64 all write the same bytes at different densities. Binary spends eight characters on a byte where hex spends two, and Base64 fits three bytes into four characters.

For the number behind a character rather than its bytes, see character codes and Unicode code points.