Every character is stored as one or more bytes (UTF-8). This tool shows each byte as 8 binary digits, two hex digits, or a decimal number from 0 to 255. Hi is 01001000 01101001 in binary, 48 69 in hex and 72 105 in decimal. Accents and emoji use several bytes each, so é becomes two. To decode, paste the codes separated by spaces; with auto-detect the tool decodes when the input looks like binary, hex pairs or decimal bytes.
A byte has eight bits, so each byte is written as eight binary digits, padded with leading zeros.
Yes. Text is encoded as UTF-8, so any character works, and decoding rebuilds the original text as long as the bytes form valid UTF-8.
See also: binary to decimal converter · Morse code translator · Base64 encoder