Resources
Format references for every supported country, the open-source tools this site is built on, and short explanations of what ID validation can — and cannot — tell you.
Country format references
Each country page documents the structure, length, and checksum rules of the national ID, straight from the validation library.
- United StatesSocial Security Number
- United KingdomNational Insurance Number
- GermanyTax Identification Number
- TaiwanNational Identification Card
- JapanMy Number
- IndiaAadhaar (UID)
Developer tools
Everything that powers this site is open source and free to use.
- Online validatorCheck a single ID number's format and checksum — it runs entirely in your browser and the number never leaves your device.
- Bulk check — coming soonA private workflow for validating lists locally in the browser is currently being prepared.
- idnumbers on npm(opens in a new tab)The MIT-licensed TypeScript library that performs every validation on this site — install it to validate IDs in your own project.
- Identique on GitHub(opens in a new tab)The source code behind the library and this website. Issues and pull requests are welcome.
Understanding ID validation
Three things worth knowing before you rely on a validation result.
Every country publishes rules for how its ID numbers are built: how many characters, which positions hold letters or digits, and which value ranges are allowed. Format validation checks a number against those published rules. It catches typos and made-up values, but it cannot tell you whether a number was ever actually issued.
Many ID schemes reserve one or more characters as a checksum — a value computed from the other characters using a fixed algorithm. If a digit is mistyped or transposed, the checksum no longer matches and the number is rejected. It is an error-detection mechanism, not a security feature.
A well-formed number with a correct checksum only proves that the number could exist. It does not prove the number was issued, that it belongs to the person presenting it, or that any document is genuine. Confirming someone's identity requires official government channels — this tool never does that.