Question 1

What are CPF and CNPJ?

Accepted Answer

They are Brazilian tax identification numbers. CPF is an 11-digit tax ID for individuals, and CNPJ is a 14-digit tax ID for legal entities. The last two digits of both are check digits calculated using the mod 11 algorithm to detect entry errors.

Question 2

Does a valid check mean the number really exists?

Accepted Answer

No. Validation only checks if the check digit matches the algorithm rules, which prevents most typos, but it does not confirm that the number corresponds to a real person or company. Actual validity must be verified with Brazilian official systems.

Question 3

Can generated numbers be used in real business?

Accepted Answer

No. The generation function produces random numbers with valid check digits for development testing, form filling, demonstration, etc. It should not be used for identity fraud or any real business. All computations are done locally in the browser; no data is uploaded.

CPF / CNPJ Validator

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