PrismKitCrypto & SecurityVAT Number ValidatorVAT Number ValidatorRuns in your browserLocalCopy linkMarkdownCheck the format and check digits of EU and UK VAT numbers offline.ISBN ValidatorVerify the check digit of an ISBN-10 or ISBN-13 and convert between the two forms.Caesar CipherShift letters with a Caesar, ROT13 or ROT47 cipher, or crack one by ranking all 25 shifts against English letter frequencies.