Caesar Cipher Encoder & Decoder – Shift Cipher, ROT13 & Atbash
Encode or decode text with the Caesar shift cipher. See ROT13, ROT47, Atbash and every shift from 1 to 25 at once – so decoding an unknown message is as simple as spotting the readable row.
🔄 31 Styles – click Copy on any result
ROT13 (encode/decode)
ROT13 (encode/decode): Attack at dawn
Shift +1
Shift +1: Attack at dawn
Shift +3 (classic Caesar)
Shift +3 (classic Caesar): Attack at dawn
Shift +5
Shift +5: Attack at dawn
Shift +7
Shift +7: Attack at dawn
Shift +10
Shift +10: Attack at dawn
Shift −3 (decode Caesar)
Shift −3 (decode Caesar): Attack at dawn
Shift −5
Shift −5: Attack at dawn
Shift −7
Shift −7: Attack at dawn
Atbash (A↔Z)
Atbash (A↔Z): Attack at dawn
ROT47 (letters, digits, symbols)
ROT47 (letters, digits, symbols): Attack at dawn
ROT18 (ROT13 + ROT5 digits)
ROT18 (ROT13 + ROT5 digits): Attack at dawn
Shift +2
Shift +2: Attack at dawn
Shift +4
Shift +4: Attack at dawn
Shift +6
Shift +6: Attack at dawn
Shift +8
Shift +8: Attack at dawn
Shift +9
Shift +9: Attack at dawn
Shift +11
Shift +11: Attack at dawn
Shift +12
Shift +12: Attack at dawn
Shift +14
Shift +14: Attack at dawn
Shift +15
Shift +15: Attack at dawn
Shift +16
Shift +16: Attack at dawn
Shift +17
Shift +17: Attack at dawn
Shift +18
Shift +18: Attack at dawn
Shift +19
Shift +19: Attack at dawn
Shift +20
Shift +20: Attack at dawn
Shift +21
Shift +21: Attack at dawn
Shift +22
Shift +22: Attack at dawn
Shift +23
Shift +23: Attack at dawn
Shift +24
Shift +24: Attack at dawn
Shift +25
Shift +25: Attack at dawn
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The Caesar cipher shifts every letter a fixed number of places along the alphabet – with a shift of 3, A becomes D and “attack” becomes “dwwdfn”. Julius Caesar reportedly used it for military messages; today it is the standard introduction to cryptography, the engine behind ROT13 on forums and the most common cipher in puzzle hunts and escape rooms.
Type plain text to encode it with any shift, or paste a coded message: because every shift from 1 to 25 is listed, one of the rows will be readable English and that is your decode. ROT13 is its own inverse (apply it twice to get back), Atbash mirrors the alphabet (A↔Z, B↔Y) and ROT47 also shifts digits and punctuation for text that must hide numbers.
How to Use This Generator
- 1
Type a message to encode, or paste ciphertext to decode.
- 2
Scan the rows – for decoding, look for the one that reads as normal language.
- 3
Copy the row you need. Tell the recipient the shift number (or “ROT13”).
How Shift Ciphers Work
Each letter is replaced by the letter n positions later, wrapping from Z back to A. Case is preserved and anything that is not a letter is left alone, so spaces and punctuation reveal word lengths – one reason the cipher is easy to break.
- Shift 3: HELLO → KHOOR
- ROT13: HELLO → URYYB → HELLO (self-inverse)
- Atbash: HELLO → SVOOL
- Decoding a shift of n is encoding with a shift of 26−n
Breaking a Caesar Cipher
With only 25 possible keys the fastest attack is to try them all, which the page does for you. If none of the rows reads clearly, the message may use a different cipher: check whether the letters are mirrored (Atbash), whether digits are involved (ROT47 / ROT18), or whether it is a substitution with a random key, which needs frequency analysis rather than shifting.
ROT13 on the Internet
ROT13 became the convention on Usenet and Reddit for hiding spoilers, punchlines and puzzle answers: it is not secret, it just stops you reading something by accident. Because 13 is half the alphabet the same operation encodes and decodes. ROT5 rotates digits (0–9) in the same spirit, and ROT18 combines the two.
Related Text Tools
Frequently Asked Questions
How do I decode a Caesar cipher without the key?
Paste the text and look through the 25 shift rows – exactly one will be readable.
What is the difference between ROT13 and Caesar?
ROT13 is a Caesar cipher with a fixed shift of 13, chosen because applying it twice restores the original.
Does it shift numbers?
Plain shifts and ROT13 leave digits alone. ROT47 shifts letters, digits and symbols; ROT18 shifts digits by 5.
Is a Caesar cipher secure?
No – it can be broken instantly. Use it for games, puzzles and spoilers, never for real secrets.
Is the tool free?
Yes.
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