Polish PESEL decoder
A Polish PESEL packs a lot of information into 11 digits: the date of birth, the person’s sex, and a check digit. This decoder reads the embedded date (the month field is offset to encode the century), determines the sex from the tenth digit, and verifies the modulo-10 checksum.
Everything runs in your browser, so the PESEL you enter is never uploaded. This is a structure and checksum decoder only — it does not confirm the number exists in the official PESEL register.