Cipher decoders: ROT13, Caesar, Vigenère, Atbash and XOR
A cipher decoder recovers plaintext from a message enciphered with a classical or obfuscation cipher — shift ciphers like Caesar and ROT13, substitution ciphers like Atbash, polyalphabetic ciphers like Vigenère, or bitwise schemes like XOR — either with a known key or by trying every key.
Classical & Obfuscated Ciphers tools
ROT13 / ROT47 Decoder
Apply ROT13, ROT18 and ROT47 rotation ciphers both ways.
Caesar Cipher Decoder
Try all 25 Caesar shifts at once and read the plaintext.
Vigenère Cipher Decoder
Decode Vigenère and autokey ciphers with a known key.
Atbash & Affine Cipher Decoder
Decode Atbash and affine substitution ciphers.
Playfair Cipher Decoder
Decrypt Playfair digraph ciphers from a keyword matrix.
Baconian Cipher Decoder
Decode Bacon's biliteral cipher from A/B groups.
Enigma Machine Simulator
Simulate M3/M4 Enigma rotors and decode messages.
Lorenz / Typex Decoder
Simulate Lorenz and Typex teleprinter ciphers.
XOR Cipher Decoder
XOR data against a key, or brute-force single-byte XOR.
Brainfuck Decoder
Execute Brainfuck and unpack JSFuck esoteric code.
Zero-Width Steganography Decoder
Extract hidden messages encoded in zero-width characters.
Which decoder do I need?
- Letters are shifted and you do not know by how much
- Caesar Cipher
- It is ROT13 (forum spoilers, puzzle hints) or ROT47
- ROT13 / ROT47
- You have a keyword and a polyalphabetic ciphertext
- Vigenère Cipher
- The alphabet looks reversed (A↔Z, B↔Y)
- Atbash & Affine Cipher
- Bytes were XORed with a short key
- XOR Cipher
- Text contains invisible characters
- Zero-Width Steganography
About classical & obfuscated ciphers decoding
Classical ciphers turn up far more often than their age suggests: in CTF challenges, geocaching puzzles, escape rooms, school assignments, spoiler-hiding on forums and in malware that uses a single-byte XOR to hide its strings. They are trivially broken by modern standards, which is exactly what makes a decoder useful — the key space is small enough to search.
Start by identifying the cipher. If only letters changed and word lengths and punctuation are intact, it is a substitution: try the Caesar brute-forcer (which includes ROT13 as shift 13) and Atbash first. If the same plaintext letter maps to different ciphertext letters, it is polyalphabetic — Vigenère is the usual suspect. A message made only of A and B groups is Baconian, and a hex or byte blob that looks random is often XOR.
Everything on this bench runs in your browser, and the brute-force tools show every candidate at once so you can spot readable English by eye.
Frequently asked questions
How do I decode a cipher without the key?
For shift ciphers, try all keys at once — the Caesar decoder shows all 25 shifts side by side. For single-byte XOR, brute-force all 256 keys. Vigenère without a key needs frequency analysis to estimate the key length first, then solve each column as a Caesar shift.
What is the difference between ROT13 and a Caesar cipher?
ROT13 is a Caesar cipher with a fixed shift of 13. Because the alphabet has 26 letters, applying ROT13 twice returns the original text, so the same operation both encodes and decodes.
How can I tell what cipher was used?
Check what is preserved. Unchanged word lengths and punctuation suggest a letter substitution. Only A/B characters suggest Baconian. Dots and dashes are Morse (an encoding, not a cipher). Uniformly random-looking bytes suggest XOR or modern encryption.
Can these tools break modern encryption like AES?
No. Classical ciphers have tiny key spaces that can be searched exhaustively. Modern ciphers such as AES are designed so that no practical search is possible; without the key, the ciphertext cannot be decoded.
Last reviewed · found a mistake? contact@decoder.tools