South African ID Number Generator

A South African ID number is always 13 digits, and unlike a purely random identifier, every digit means something. The first six (YYMMDD) are the holder's date of birth. Because the year is only two digits, the century has to be inferred: a common convention (the one this tool uses when validating) is to assume the more recent century when the two-digit year is less than or equal to the current two-digit year, and the older century otherwise.

The next four digits are a sequence number, and this is where gender is encoded: values from 0000 to 4999 indicate female, and 5000 to 9999 indicate male. After that comes a single citizenship digit, 0 for a South African citizen or 1 for a permanent resident. The digit after that was historically used to indicate race under apartheid-era regulations and has been fixed at 8 for every ID issued since the current format was standardised, so it no longer carries meaning.

The final digit is a checksum, calculated with a Luhn-style algorithm over the first twelve digits. It sums the digits in odd positions, doubles the number formed by the digits in even positions and sums those digits too, and derives a check value from the total. This is what lets a signup form reject a mistyped ID number before it ever reaches a database, and it is exactly what the validator above checks.