Generate mathematically valid CPF numbers for software tests, with check-digit explanation and no registry lookup.
Developers and testers constantly need CPFs that "pass" a form's validation without using a real person's document. That is exactly what this tool does: it draws nine base digits and computes the two check digits with the modulo-11 rule, producing a number that is mathematically consistent but fictitious. It is for filling test fixtures, populating staging databases, building mocks and illustrating documentation. What it does not do is query the Receita Federal or confirm that anyone exists, a CPF that is valid by the math may not be assigned to anybody. Everything is generated in your browser, and the number never goes to analytics.
A CPF has 11 digits: nine base digits plus two check digits at the end. The ninth base digit indicates the fiscal region where the CPF was issued (for example, 8 = SP, 7 = ES/RJ), which the tool shows next to the number. The last two are computed from the previous ones to catch typing errors.
The calculation uses modulo 11: each base digit is multiplied by a decreasing weight, the products are summed, and the check digit comes from the remainder of that sum divided by 11 (with the convention that a remainder of 0 or 1 becomes digit 0). It is the same rule form validators apply, which is why the generated number passes them.
In development, the typical use is filling forms and flows that require a well-formed CPF: customer registration, checkout, onboarding. With a number that passes digit validation, QA can test the happy path without depending on real data and without violating anyone's privacy.
It is also useful for populating test data (seeds/fixtures) in staging databases, for examples in documentation and tutorials, and for demos. In all of these, the number serves as a coherent placeholder, not as an identity.
Even when the goal is testing, a CPF is a sensitive identifier in Brazil and protected by the LGPD when tied to a person. That is why the tool generates everything locally and avoids putting numbers in URLs, storage, logs or analytics, a good practice you should follow in your environments too.
When you need to validate a real CPF typed by a user, use the math-validation tool and keep the same caution: validating checks the digit rule, it does not query a registry or prove ownership. Generating synthetic data for testing is legitimate; using a number to impersonate someone or commit fraud is a crime.
Paste the code into your HTML and the tool shows up on your page, without J-Kit's navigation and ads. It still runs in the browser of whoever visits your site.
<iframe
src="https://jkit.tools/embed/en-US/cpf-generator"
width="100%"
height="600"
style="border:0"
loading="lazy"
title="CPF Generator"
></iframe>These references help contextualize formulas, standards, APIs and limitations used on this page. They do not replace professional validation when a result has legal, financial, medical or operational impact.
There is no such guarantee, in practice, it almost certainly is not. The tool only guarantees the mathematical consistency of the check digits; it does not query the Receita Federal or verify whether the number is assigned to anyone. Always treat it as fictitious data.
The tool draws nine base digits and computes the two check digits with the modulo-11 rule used by form validators. This creates mathematical consistency, not a real identity.
The number is generated locally in the browser. Analytics receives only action, status, type and format, never the generated CPF.