Checkers online tools — same implementation for humans and agents · 34 tools
root:checker·Human page + Agent API · same engine
MD5 + SHA-256 checksums for text
node:crypto
WCAG contrast ratio and AA/AAA pass/fail
wcag-contrast
Perceptual color difference via culori CIEDE2000 with Lab/OKLCH
culori
Luhn algorithm check for card numbers (offline, never stored)
luhn
Authority-zone system-DNS recursive capture + multi-resolver + browser DoH/WebRTC; honest degrade when no hits, no fake Geo/ASN
node:dns.Resolver+browser-probes
Resolve A/AAAA/MX/TXT/NS/CNAME (Node dns; answers from the Forge host resolver)
node:dns
Validate or calculate the GS1 check digit in bulk: GTIN-8/12/13/14, SSCC-18, GLN-13
gs1-mod10
Validate email format (batch, one per line)
email-shape
Compare two .env files by key, not by line: added / removed / changed / commented-out, with secret redaction that still reports whether the secret changed
nebutra-dotenv-parity
Checksum Base64 file payloads
node-crypto
Match a file's leading bytes against 180 signatures to name its true format; ZIP/ISO-BMFF/OLE2 containers are opened for real, and a lying extension is tiered benign / mismatch / high-risk
nebutra-magic-table
Constant-time compare two hashes or secrets
timing-safe-equal
Verify HMAC-SHA256 signature matches payload
crypto.createHmac
Validate an IBAN per ISO 13616: structure, per-country length and the MOD 97-10 check digits (offline, never stored)
iban-mod97
Validate CN resident ID check digit (GB 11643)
gb11643
Validate IPv4 / IPv6 format offline
ip-regex
Bulk-validate ISBN-10/ISBN-13 check digits, suggest the correct one, convert 10↔13
isbn-check-digit
Validate, pretty-print, or minify via JSON.parse with line/column errors; optional sortKeys
JSON.parse
Validate JSON against JSON Schema via Ajv
ajv
Compute MD5 hex digest (legacy checksum only)
node-crypto
Lookup common MIME types by file extension
mime-table
Generate MD5, SHA-1, SHA-256, SHA-512 in one call
node:crypto
Show client IP and key headers as seen by Forge (host-injected; no fake geo)
request-headers
Estimate password entropy bits from charset size
charset-entropy
Estimate password strength with zxcvbn-ts
zxcvbn-ts
Regex match/replace with timeout guard against ReDoS
RegExp+timeout
SHA-1 digest (legacy)
node-crypto
Compute SHA-256 hex digest of text
node-crypto
SHA-512 digest via node:crypto
node-crypto
Connect to host:443 and read subject, SANs, validity, fingerprints
node:tls
Field-level validation of China's 18-character unified social credit code per GB 32100-2015 (ISO 7064 MOD 31-3 check digit, GB/T 2260 division, department and category tables), plus seeded reproducible test-code generation
gb32100-uscc
Parse and validate URL shape (WHATWG URL)
URL
Validate UUID format and version nibble (RFC 4122)
uuid-shape
Validate a 17-character VIN against 49 CFR 565.15 / ISO 3779: length, character set (no I/O/Q) and the position-9 check digit, with the position-by-position math
vin-check-digit
