5 Validation Tools Every Developer Uses Daily (And Didn’t Know Were Free)
You just wired €5,000 to the wrong IBAN. The German bank returned it with a €15 fee. You spent 20 minutes on the phone with your finance team trying to figure out what went wrong.
The answer: the IBAN was valid format, invalid checksum. No tool caught it before you sent.
That’s the gap ElysiaTools fills.
The Tool You Didn’t Know You Had
ElysiaTools is a collection of over 1,600 free browser-based tools for developers. No signup, no API key, no rate limits. Open the URL and you’re working.
The one that stopped me: Credit Card Validator. Paste `4111111111111111` (Visa’s test card) and it runs the Luhn algorithm, identifies the card type, checks the IIN/BIN range, and breaks down every component—MII digit, BIN prefix, account number, check digit. MasterCard, Amex, Discover, China UnionPay, JCB, Diners Club, Maestro. All handled automatically.
That lookup you were paying $0.10 per check for? Free. Unlimited.
How Developers Actually Use These Tools
Catching credit card errors before Stripe charges you fees. You have a checkout form. Before sending a card to your payment processor, you run it through Credit Card Validator to catch typos and fabricated numbers early. The Luhn check alone catches 90% of entry errors before they generate failed transaction fees.
Validating IBANs before international wire transfers. Sending €5,000 to a client in Hamburg? Paste their IBAN into IBAN & SWIFT Validator first. It checks country-specific length (German IBANs must be exactly 22 characters), verifies the checksum using the modulo-97 algorithm, and decomposes the BBAN into bank code and account number. A wrong IBAN gets returned with a retrieval fee. This catches that before you send.
Catching SemVer mistakes before your CI breaks. Your release pipeline fails because someone pushed `01.1.0` instead of `1.1.0`. Leading zeros violate SemVer 2.0.0 spec. The SemVer Validator flags exactly what went wrong—the major version field has a leading zero—and explains why it’s invalid. No more vague “invalid version” errors.
Cron expression debugging before your job fires at the wrong time. `*/5 * * * *` fires every 5 minutes. `0 */5 * * *` fires at minute zero of every fifth hour. One character changes the entire schedule. The Cron Expression Validator shows the human-readable description, next 5 run times, and warns when both day-of-month and day-of-week are specified—a common mistake that causes unexpected behavior in most cron implementations.
VIN validation for automotive integrations. Vehicle Identification Numbers are 17-character strings with an embedded check digit. If you’re building a car dealership portal, insurance quote tool, or fleet management dashboard, the VIN Validator confirms format, length, and checksum in one paste.
Why This Isn’t in Your Toolkit Yet
Nobody writes blog posts about validation tools. There’s no “top 5 credit card validators” comparison. No Product Hunt launch. These tools exist because someone needed them, built them, and left them running. No marketing, no SEO, no influencer mentions.
For developers building anything that touches financial data—fintech apps, e-commerce platforms, logistics systems—these validators are infrastructure. The real win is the library: VIN today, tracking number tomorrow, all in the same place, no tabs, no ads.
The Missing Feature
Intelligent auto-detection across the full toolset. Paste in an unknown string and get back: “this is a German IBAN, this is a VIN with an invalid check digit, this is not a valid credit card.” Right now you need to know what you’re looking for to find it. That’s the gap worth filling.
Until then: Credit Card Validator · IBAN & SWIFT Validator · SemVer Validator · VIN Validator · Cron Expression Validator.
One URL. All of them. Free.
