I like small projects that solve one clearly defined problem and then have the decency to stop. The IBAN validator is exactly that: a tool that tells you whether an International Bank Account Number is structurally valid. Not whether there's money in it. We'll get to that.
What it actually does
The validator checks an IBAN against the formal rules of the standard — the right length for the country, the right shape, and most importantly the mod-97 checksum (ISO 13616). It's the same algorithm most developers first meet on Wikipedia, and the genuinely interesting part wasn't the math. It was making the implementation fast, correct, and easy to test against IBANs from a dozen countries without it falling over.
What it very much does not do
Here's the honest part, in big friendly letters: it validates structure, not existence. The tool can tell you an IBAN is formally plausible. It cannot tell you the account is real, open, or has more than €4.20 in it. That's not a missing feature — it's a hard limit. Without a direct line into the banking system, structural validation is the entire ceiling, and anyone promising more is selling something.
Why bother building it?
Because this is the kind of project that goes from idea to working result in an afternoon, as long as you actually understand the constraints. There's no sprawling scope, no "phase two," no creeping ambition. You implement a known algorithm cleanly, you test it properly, and then you walk away. That restraint is the whole skill.
The takeaway
This validator will never be groundbreaking, and that's the point. It solves a precise problem, states its limits out loud, and was a satisfying exercise in implementing something correctly rather than impressively. Projects like this are usually worth more as engineering practice than as products — and honestly, that's fine by me.
// Try it yourself: the IBAN validator lives with the rest of my mini-APIs.