CPF Validator
Quickly and easily validate your CPF! Our CPF validator ensures the authenticity of the provided number, confirming that it is valid and error-free. If you need to generate a new CPF, try our CPF generator.
How CPF Validation Works
What does the validator check?
The Help4Dev CPF validator checks whether a given number is mathematically valid according to the official Receita Federal algorithm. It does not query government databases — meaning it does not check if the CPF is active, belongs to a real person, or is in good standing. The validation only confirms that the check digits (the last 2) were correctly calculated from the 9 base digits.
When is a CPF considered invalid?
A CPF is invalid when: (1) it has fewer or more than 11 digits; (2) all digits are the same (e.g. 111.111.111-11, 000.000.000-00), as these are rejected even if mathematically consistent; (3) the check digits do not match the expected calculation by the modulus 11 algorithm. The validator detects any of these situations and reports immediately.
Why use validators in development?
Systems that accept CPF as input — e-commerces, banks, government platforms, health systems — need to validate the format before processing. Testing validation logic requires both valid and invalid CPFs. The Help4Dev validator allows you to quickly check whether a specific number is valid by the algorithm, making it easy to create test cases covering both success and error scenarios.