Rotate each letter by 13 positions. Since the alphabet has 26 letters, applying ROT13 twice returns the original text.
Input letters only shifted — numbers & symbols preserved
Output
ROT13 shifts each letter by 13 positions (A→N, B→O, …, Z→M). Because 13 + 13 = 26 (the length of the alphabet), encoding and decoding are the same operation. Non-alphabetic characters pass through unchanged.
Caesar Cipher
Substitution cipher that shifts every letter by a fixed number of positions in the alphabet.
Shift Amount
Shift: 13
Input case preserved — non-letters unchanged
Output
Caesar cipher — classic substitution cipher used by Julius Caesar. Encrypting shifts each letter forward by the key; decrypting shifts it back. Shift 13 is equivalent to ROT13. There are only 25 meaningful keys, making brute-force trivial.
Vigenère Cipher
Polyalphabetic substitution cipher that uses a repeating keyword to vary the shift for each character.
Keyword letters only, A-Z
Input case preserved — non-letters pass through
Output
Vigenère cipher — each letter of the plaintext is shifted by the corresponding letter of the keyword (A=0, B=1, …, Z=25). The keyword repeats cyclically. Much stronger than Caesar, but still vulnerable to frequency analysis when the key is short.
Atbash Cipher
Ancient Hebrew cipher that maps the alphabet to its reverse mirror: A↔Z, B↔Y, C↔X, and so on.
Input symmetric operation — encode = decode
Output
Atbash cipher — maps each letter to its mirror across the alphabet (A↔Z, B↔Y, …). Originally used for the Hebrew alphabet; here applied to the Latin alphabet. Completely symmetric: applying it twice returns the original text.
Morse Code
International Morse Code encoder and decoder using Unicode dot (·) and dash (−) characters.
Input text for encode | morse for decode (· or . for dot, − or - for dash, / for word break)
Output
Morse code — uses · (dot) and − (dash). Characters are separated by a single space; words by /. When decoding, both ASCII . / - and Unicode · / − are accepted.