About decimal and octal

Decimal is base 10 — ordinary numbers. Most code displays values in decimal even when they're stored as bits underneath, so it's usually one side of any base conversion.

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.

For example, decimal 1024 is 2000 in octal. The converter uses BigInt, so numbers of any size convert without losing precision — and it all runs in your browser.