Overview
Security and identity validation covers a wide range of formats, but they share a common theme: getting the format wrong doesn't just produce an error message, it can mean lost funds, a rejected transaction, or a false sense of security about a device or account. This guide covers validators for passwords, government and device identifiers, and payment and cryptocurrency formats where structural correctness is the first line of defense against a class of costly mistakes.
It's worth being explicit about what format validation can and can't tell you in this category specifically: every validator below confirms a value is structurally well-formed according to its published standard, not that it's currently active, unblocked, or free of fraud — those checks require a live lookup against the issuing authority or network, which is a separate step from the format validation covered here.
Step 1: Check Password Strength
The Password Strength Validator evaluates character diversity, checks against known common-password and dictionary-word lists, and estimates entropy — a measure of how resistant the password is to automated brute-force guessing. Length alone is a weak signal of strength; a long password built from a predictable pattern or a well-known phrase can score poorly, while a shorter password with genuine random variety across character types can score better, which is why entropy estimation matters more than character count alone.
Step 2: Validate an AAMVA Driver's License Barcode
The AAMVA Barcode Validator checks the structure of PDF417 barcodes printed on US and Canadian driver's licenses, which encode name, address, date of birth, and license details in a standardized field format defined by the American Association of Motor Vehicle Administrators. This matters for age-verification systems, ID-scanning kiosks, and retail or venue check-in tools that need to confirm scanned barcode data actually follows the expected AAMVA structure before trusting the decoded information.
Step 3: Validate Amex and Discover Card Formats
The Amex/Discover Validator checks card number length, starting digit pattern, and the Luhn checksum used across all major card networks to confirm a card number is structurally valid. This is a format check only — it can't confirm the card is active, has available credit, or hasn't been reported lost or stolen, all of which require a live authorization check against the card network rather than a client-side validation step.
Step 4: Validate a Cryptocurrency Wallet Address
The Crypto Address Validator checks wallet address formats per blockchain network — Bitcoin addresses use Base58Check or Bech32 encoding starting with 1, 3, or bc1 depending on address type, while Ethereum addresses are 42-character hexadecimal strings starting with 0x. Since cryptocurrency transactions are generally irreversible once confirmed, and sending funds to a validly-formatted address on the wrong network typically results in permanently lost funds, checking the address format against the specific network you're actually sending on is one of the few pre-transfer safeguards available.
Step 5: Validate an FCC ID
The FCC ID Validator checks the grantee-code-plus-product-code structure assigned to electronic devices sold in the US that emit radio frequency signals — WiFi routers, Bluetooth accessories, cordless phones, and similar equipment. A structurally valid FCC ID can then be looked up in the FCC's public equipment authorization database to confirm a device was actually tested and certified, which is a useful step when buying electronics from an unfamiliar seller or verifying a product listing's claims.
Step 6: Validate an IMEI Number
The IMEI Validator checks the 15-digit International Mobile Equipment Identity format using the Luhn checksum algorithm, the same general-purpose checksum used for credit card validation. This is a useful first screen when buying a used phone — a structurally invalid IMEI is an immediate red flag — though a valid format alone doesn't confirm the specific device hasn't been reported lost or stolen, which requires a separate carrier or manufacturer blacklist check.
Step 7: Know Where Format Validation Stops and Real Verification Starts
Every validator in this guide answers one question — "is this value structurally well-formed?" — and stops there by design. A password validator can't check whether that exact password has already leaked in a data breach. A crypto address validator can't confirm the address belongs to who you think it does. A card format validator can't confirm the card is currently active. Each of these deeper checks requires a live lookup against the issuing bank, blockchain network, breach database, or carrier — a fundamentally different kind of check than confirming a string matches a published format specification.
Treating format validation as the first filter rather than the final answer is the right mental model across this entire category: catch the malformed, obviously-wrong entries cheaply and instantly at the format-check stage, then reserve the slower, authoritative lookup for values that have already passed that first filter.
Key Terms
- Luhn Algorithm — a general-purpose checksum formula used to catch common data-entry errors, applied across credit card numbers, IMEI numbers, and several other identifier formats
- Entropy (Password Strength) — a measure of how unpredictable a password is, expressed as the estimated number of attempts a brute-force attack would need to guess it
- PDF417 Barcode — a stacked linear barcode format capable of encoding significant structured data, used on AAMVA-compliant driver's licenses and ID cards
- Base58Check / Bech32 — two address encoding formats used by Bitcoin, distinguished by which characters and prefixes they use and which era of the Bitcoin protocol introduced them