CPF validator

A CPF has 11 digits, the last two being check digits computed from the first 9 via an algorithm called mod-11.

For the first check digit: - Each of the first 9 digits is multiplied by weights descending from 10 to 2 - The results are summed - The sum is multiplied by 10 and the remainder of the division by 11 is taken - If the remainder is 10, the digit is 0

For the second check digit, the process is repeated including the first check digit, with weights from 11 to 2.

This validator implements exactly that algorithm. If you want to go beyond validation and check whether a CPF has Brazilian court cases, use Vigilant — same CPF, but now we are talking court data, not just mathematical validation.