Free tool
CPF validator
Check whether a Brazilian CPF is valid in one click. The computation runs entirely in your browser — nothing is sent to any server.
How the algorithm works
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.
Frequently asked questions
How does the CPF mod-11 algorithm work?
A CPF has 11 digits — the last 2 are "check digits" calculated from the first 9. For the 1st check digit: multiply each digit by decreasing weights from 10 to 2, sum, multiply by 10, take mod 11 (if remainder is 10, digit becomes 0). For the 2nd digit: repeat including the 1st check digit with weights 11 to 2. If both match, the CPF is mathematically valid.
Does a mathematically valid CPF mean it was actually issued?
No. Passing mod-11 only guarantees the check digits are consistent — but the CPF may never have been issued by Receita Federal. To validate real existence (registration status, associated name, etc.), real-time lookup against the Receita portal is required (paid service). This tool only does mathematical validation.
Does this validator send the CPF to any server?
No. 100% of the computation runs in your browser via JavaScript — no data is sent to TrackJud or third-party servers. You can open DevTools → Network → confirm there are no requests when validating a CPF. Safe to use with sensitive data.
Do CPFs with repeated digits (111.111.111-11) pass mod-11?
Mathematically yes — sequences like 111.111.111-11 and 222.222.222-22 pass the mod-11 algorithm, but Receita Federal never issued those numbers. This validator automatically detects and rejects all 10 repeated sequences to avoid false positives in tests and forms.
Can I validate many CPFs in batch?
This tool validates one CPF at a time. For bulk validation (hundreds/thousands), use the Vigilant API — it runs mod-11 validation before any court lookup, rejecting invalid CPFs on input. More efficient than a manual script and integrated with the lawsuit query flow.
Related tools
Need to go beyond validation?
Vigilant searches lawsuits linked to a CPF across 12 Brazilian court sources. Via API or via the dashboard.
Search lawsuits with Vigilant