Check the format, check digit and encoded birth date of a Polish PESEL number - entirely locally in your browser, no upload.
Running locally on your device ...
Running locally on your device ...
0%
Your files never left your device
No. Everything runs in your browser - your file never leaves your device. How this is verifiable
The PESEL number (Powszechny Elektroniczny System Ewidencji Ludności) is Poland's 11-digit personal identifier. The first 6 digits encode the birth date (with a month offset that also distinguishes the century), the next 3 are a running serial, the 10th digit's parity encodes sex, and the 11th is a weighted check digit. This tool splits the number, recomputes the check digit and decodes the birth date and sex - purely by calculation, from the publicly documented encoding logic.
Paste the number (spaces and dashes are ignored) and you get an instant result: valid or invalid, with a reason - wrong format, a date that does not exist, or a wrong check digit. If the structure checks out, the result also shows the decoded birth date and sex.
The whole check runs locally in your browser in pure JavaScript - the entered number is not uploaded, not stored, and no foreign library is loaded from a CDN. That matters especially for a number that, in Poland, is treated as a specially protected personal data item.
| Input formats | Text input |
|---|---|
| Output format | TXT |
| Batch processing | No |
| Processing | Locally in your browser (JavaScript) |
| File upload | None |
Limitations: This tool performs only a mathematical checksum/format check. It is not an official identity, existence, or registry verification and not a request to any authority. Any additional information derived from the number's structure is based solely on the publicly documented encoding logic of the issuing authority. The serial digits (positions 7-9) historically carried a regional hint; this tool deliberately does not evaluate it.
No. The check runs entirely locally in your browser; the number never leaves your device and is not stored.
No. It only checks whether the structure and the check digit are mathematically correct - no query against the PESEL registry or any authority.
It is decoded purely by calculation from the first 6 digits of the PESEL number - the publicly known encoding logic of the Polish authorities, not from a registry lookup.
The tool names the reason: wrong length, a non-existent date, or a wrong check digit - never a made-up "valid".
Yes. After the first load, the check works entirely without an internet connection.
Check a NIP/REGON number · Calculate a checksum · Decode JWT · Poland Salary Calculator