Converts between text and its numeric forms — decimal, hexadecimal, binary, octal and Base64 — in either direction. Values are UTF-8 bytes by default (so é is two bytes) or Unicode code points; hex/binary strings without separators are split into bytes automatically and 0x/0b/0o/\x/&#x prefixes are tolerated on input. Output separators, prefixes and hex case are configurable; invalid digits, out-of-range values and byte sequences that are not UTF-8 are reported. Everything runs locally.