About octal and hex

Octal is base 8, using digits 0–7. Each octal digit maps to exactly three bits, which is why Unix file permissions like 755 are octal. Code writes it with a 0o prefix.

Hexadecimal is base 16 — digits 0–9 then a–f. One hex digit is exactly four bits, so bytes read as tidy two-digit pairs. Colors, memory addresses, and hashes are all conventionally written in hex with a 0x prefix.

For example, octal 755 is 1ed in hex. The converter uses BigInt, so numbers of any size convert without losing precision — and it all runs in your browser.