The number base converter parses base 2–36 digits one at a time itself and accumulates a BigInt, so integers are not limited by JavaScript's 53-bit safe integer range. Automatic mode recognises base 16, 2 and 8 from the 0x, 0b and 0o prefixes only; without a prefix it assumes decimal.

1. 01Enter an integer and choose the source base, or use automatic mode to detect the common prefixes.
2. 02Read the quick results in base 2, 8, 10 and 16.
3. 03Choose any target base from 2 to 36.
4. 04Digit grouping and uppercase letters can be toggled; copying removes the grouping spaces automatically.

• Only integers are supported; decimals, scientific notation and fixed-point base conversion are not.
• Spaces, underscores and commas are stripped from the input; the legal source characters are 0–9 and a–z, case-insensitively.
• Automatic mode does not guess the base from the digits: FF without 0x is still read as decimal and reports an illegal character, so base 16 has to be chosen manually.
• A negative output is explicitly “minus sign plus magnitude”, not a fixed-width two's complement, so it cannot be used directly to derive the bit patterns of int8 or int32.
• Grouping shows every 3 digits for base 8 and 10 and every 4 for the rest; it is a readability format only and does not change the value.

Integers are computed locally in the browser with BigInt; nothing is uploaded and nothing is saved.