Knowledge Base
In-depth articles on validation algorithms, GDPR compliance and the engineering details behind the generators on this site. Written for developers, QA engineers and anyone who works with test data.
IBAN MOD-97 Explained
How modulo 97 validation works mathematically, a TypeScript reference implementation, why MOD-97 instead of Luhn, and benchmarks comparing BigInt against the chunked-modulo trick.
GDPR-Compliant Test Data: A Practical Guide
Why fictional data matters under GDPR Articles 5 and 25, real fines that involved test or production data misuse, do's and don'ts, and a decision flowchart for choosing the right approach.
The Luhn Algorithm for Credit Cards
Mathematical explanation of the Luhn checksum, history (IBM 1954), a TypeScript implementation, why Luhn does not prove validity, the card networks that use it, and test card numbers per issuer.