ID & Number Validators
39 free id & number validators tools in the Developer Tools collection — every one runs in your browser with no signup and no uploads.
Clipboard Contents Security Checker
Read your clipboard (with permission) and scan it for secrets, tokens, and PII before you paste
CONTRIBUTING.md Builder
Generate contributor guidelines for your open source project
CORS Header Explainer & Validator
Paste CORS response headers and get a plain-English breakdown of what they allow
Damm Algorithm Checker
Validate numbers using the Damm totally antisymmetric quasigroup
Data URI Inspector & Security Checker
Decode any data URI and flag potentially dangerous MIME types or obfuscated payloads
EAN-13 / UPC-A Barcode Validator
Validate EAN-13 and UPC-A barcodes and compute check digits
Folder Listing Diff
Paste two directory listings and find files added, missing, or renamed
HSTS Header Checker
Paste a Strict-Transport-Security header and verify max-age, subdomains, and preload
IMEI Number Validator
Validate mobile device IMEI numbers via Luhn algorithm
IP Address Type & Privacy Checker
Classify any IPv4/IPv6 address as public/private/loopback/reserved/documentation
IP (Ingress Protection) Rating Lookup
Decode IEC 60529 IP codes for dust and water protection
ISBN-10 to ISBN-13 Converter
Convert any valid ISBN-10 to its ISBN-13 equivalent
ISBN-10 Validator & Check Digit
Validate ISBN-10 and compute missing check digits
ISBN-13 Validator & Check Digit
Validate ISBN-13 (EAN-13) and compute missing check digits
ISO-8859-2 / Latin-2 Encoder
Show Central European Latin-2 byte values for text in hex
ISO-8859-1 / Latin-1 Encoder
Encode text to an ISO-8859-1 byte sequence shown as hex
Luhn Algorithm Checker
Validate credit card numbers and IMEI via Luhn mod-10
Luhn Algorithm Checker
Validate card numbers with the Luhn mod-10 check and generate test numbers.
OpenAPI / Swagger Spec Validator
Validate an OpenAPI 3.x or Swagger 2.0 YAML or JSON spec in your browser.
Passport Validity Requirement by Destination
Minimum passport validity required to enter each country
API Rate-Limit Header Calculator
Design a rate-limiting policy and preview the X-RateLimit headers it would produce.
RSS / Atom Feed Validator
Validate a pasted RSS 2.0 or Atom 1.0 feed for spec compliance
Same-Origin Policy Checker & Explainer
Enter two URLs and instantly see whether they share an origin, with a full explanation
SPF Record Builder & Syntax Checker
Build a valid SPF TXT record from a guided UI and validate the syntax offline
Verhoeff Checksum Checker
Validate digits using the dihedral group Verhoeff algorithm
Text Diff Checker
Compare two blocks of text line by line and highlight every change.
Luhn Algorithm Checker
Validate any number with the Luhn (mod-10) checksum.
IBAN Validator
Check any IBAN with the ISO 13616 mod-97 algorithm.
Credit Card BIN Checker
Identify the card network from a BIN / IIN prefix.
EU VAT Number Validator
Check the format of any EU VAT number — all 27 member-state patterns.
ISBN Validator
Validate ISBN-10 and ISBN-13 check digits and convert between them.
Semver Range Checker
Check whether a version satisfies an npm semver range like ^1.2.0.
Ukraine INN Validator
Decode a Ukrainian tax number (RNOKPP) — date, gender and checksum.
Austria SVNR Validator
Decode an Austrian social-security number — date and check digit.
Keyword Density Checker
Count word frequency and density in any text to avoid keyword stuffing.
IEEE 754 Floating-Point Converter
Decimal to IEEE 754 single and double precision bits.
Credit Card Validator
Luhn checksum plus card-brand detection — all in your browser.
Malaysia MyKad Validator
Validate a 12-digit MyKad number: date, place of birth, gender and serial.
North Macedonia EMBG Validator
Validate a Macedonian EMBG and decode birth date, gender and region.