APIShedNo sign-inValidates PESEL/NIP/REGON/IBAN/Luhn/ISBN/EAN/SWIFT-BIC/VAT; RPN calc, date math, hashing, tokensChecksum ValidatorNo sign-inValidates Luhn, IBAN, ISBN, EAN/UPC, SWIFT/BIC, and EU VAT checksums and formats.Date Math CalculatorNo sign-inDate arithmetic: day differences, business days, age, leap years, day-of-week, add/subtract.Hash Digest ToolNo sign-inComputes MD5, SHA1, SHA256, SHA512, and CRC32 digests from text, base64, or hex input.PESEL/NIP/REGON ValidatorNo sign-inValidates Polish PESEL, NIP, and REGON checksums; PESEL also decodes birth date and sex.Regex/Email/URL ValidatorNo sign-inRegex matching, email/URL format validation, and JSON Schema validation.RPN CalculatorNo sign-inEvaluates Reverse Polish Notation (postfix) expressions: arithmetic, trig, logs, bitwise ops.Text ToolsNo sign-inExact character/word counting, reversal, palindrome checks, indexing, sorting; Unicode-safe.Token CounterANo sign-inCounts tokens under OpenAI-compatible (tiktoken) encodings, by model or encoding name.