# 8 Free Security Validation Tools That Catch What Your Code Misses
Your checkout form takes “123456” as a valid password. A credit card number with four transposed digits sails through. Somewhere in your database, a sits waiting for its moment.
None of this requires a skilled attacker. It just requires a user who types the wrong thing. And then you spend a week tracking a failed payment, a corrupted record, or a script running in someone else’s browser.
These eight free tools close the gaps before they become incidents.
Credit Card Validator
Most checkout forms accept anything that looks plausible and fail somewhere downstream. The Credit Card Validator catches bad numbers at the door. It runs the Luhn checksum — the same algorithm every payment processor uses — and identifies the card type (Visa, MasterCard, Amex, UnionPay) before the transaction starts.
A single transposed digit doesn’t just decline the charge. On some processors it triggers a fraud hold, which means a customer calls support and someone spends an hour untangling it. Validating at the edge prevents both.
The tool strips spaces and dashes automatically, so users can paste formatted or unformatted numbers without reformatting.
Strong Password Validator
“Password123!” passes most forms. It shouldn’t. The Strong Password Validator checks what actually matters: length, mixed case, numbers, special characters, and pattern detection for keyboard walks, sequential numbers, and dictionary words.
It gives per-rule feedback — not a vague “weak password” warning, but “your password contains a keyboard pattern” or “minimum length is 12 characters.” Users fix what they can see.
If your organization still forces 90-day password rotation, stop. NIST explicitly recommends against it — the policy produces weaker passwords and trains users to pick incrementally predictable sequences. Enforce strength once at creation, not complexity through rotation.
SQL Injection Detector
SQL injection powered breaches at Ticketmaster, Synamedia, and hundreds of smaller targets. The pattern never changes: unsanitized input reaches a database query, and an attacker uses that gap to execute their own commands.
The SQL Injection Detector scans for seven categories of injection patterns: SQL keywords (SELECT, DROP, UNION, EXEC), conditional injections (‘ OR ‘1’=’1), time-based blind injection (SLEEP(), WAITFOR DELAY), and UNION-based SELECT attacks. It assigns risk levels from LOW to CRITICAL.
A CRITICAL result is a textbook injection payload. A MEDIUM result looks harmless to a human but contains patterns that become dangerous when concatenated into a query. That’s where most leakage happens — the code passed every review because no one thought to test it with a single quote.
XSS Payload Detector
Cross-site scripting steals session cookies, defaces pages, and redirects users. It starts with an input field that accepts 
The XSS Payload Detector catches ten categories of XSS patterns: script tags, JavaScript and VBScript protocols, event handlers (onload, onerror, onclick), iframe injections, SVG-based attacks, encoded payloads (URL encoding, HTML entities), and polyglot exploits that work across multiple parsers simultaneously.
Run it against any field that accepts freeform user input — comments, bios, product reviews, support messages. Anywhere text reaches your front end is an XSS surface.
IBAN & SWIFT Validator
One wrong digit in an IBAN routes money to the wrong account. Retrieving it takes three to six weeks. The bank charges a reversal fee on top.
The IBAN & SWIFT Validator checks the modulo-97 checksum on IBANs and validates SWIFT/BIC codes before the transfer starts. It identifies the issuing bank and country, so routing fails fast instead of timing out downstream.
For any system that moves money across borders, this belongs in the pre-submit checklist — not in the error log after a failed transfer.
VIN Validator
A Vehicle Identification Number contains a checksum in its 17th character. Transposed digits, invalid characters, and fabricated VINs all fail it. The VIN Validator catches these before a vehicle enters your system.
This matters for automotive marketplaces, insurance underwriting, and fleet management. Registering a policy to the wrong VIN — or listing a vehicle whose registration doesn’t match the listing — creates disputes that are difficult to unwind after the transaction closes.
ISBN Validator
Books use two formats: ISBN-10 (10 digits, modulo-11 checksum) and ISBN-13 (13 digits, modulo-10 checksum). The ISBN Validator handles both, checks the checksum, and flags numbers that cannot exist in either format.
Library systems, bookstore inventory, and publishing tools all use ISBNs as a primary key. A bad digit breaks lookups, breaks syncs, and corrupts reports. One validation call costs less than debugging a broken import.
Passport Validator
Passport numbers follow country-specific rules that encode the issuing authority and passport type. The Passport Validator validates formats for China, USA, Japan, and most major issuing countries.
For travel booking platforms, visa systems, and identity verification workflows, accepting a malformed passport number means downstream failures that cost more to fix than the validation would have.
The One Question to Ask Your Code
Every one of these tools answers the same question: what happens if someone types the wrong thing?
In most systems, the answer is “it depends on where that input ends up.” That’s the problem. The further a bad input travels, the harder it is to find and the more damage it does.
Validation at the edge — at the point where data enters your system — turns an expensive mystery into a clean error message. It protects your database, your users, and your support team.
What will your code reveal when you run these eight checks? Every system that runs the SQL injection detector finds payloads in places that looked safe on a code review. Every site that runs the XSS detector finds stored scripts in fields that seemed harmless. The question is whether you want to find those inputs now — when fixing them costs nothing — or later, when they cost something. (All tools are free at ElysiaTools.)
