About the Caesar Cipher & ROT13
Shift letters with the classic Caesar cipher, apply ROT13 or ROT47, or brute-force an unknown shift by listing all 25 possibilities. Great for puzzles, geocaching and learning cryptography basics.
Key features
- ROT13: encode and decode with the same click
- Caesar cipher with any shift from −25 to 25
- ROT47 for letters, digits and symbols
- Brute force: list all 25 shifts to crack a message
- Keeps upper/lowercase, spaces and punctuation
- Instant results as you type
Shift letters to encode and decode
The Caesar cipher is one of the oldest known ciphers: Julius Caesar reportedly used a shift of 3 for military messages. Today it's used for puzzles, geocaches, escape rooms, spoiler hiding (ROT13) and teaching the basics of cryptography.
Shift table (shift 3)
| Plain | A | B | C | D | E | … | X | Y | Z |
|---|---|---|---|---|---|---|---|---|---|
| Cipher | D | E | F | G | H | … | A | B | C |
Examples
| Cipher | Input | Output |
|---|---|---|
| ROT13 | Hello, World! | Uryyb, Jbeyq! |
| Caesar +3 | attack at dawn | dwwdfn dw gdzq |
| Caesar −3 | dwwdfn dw gdzq | attack at dawn |
| ROT47 | Hello 123 | w6==@ `ab |
ROT13 vs ROT47
| ROT13 | ROT47 | |
|---|---|---|
| Changes | Letters A–Z | All printable ASCII (! to ~) |
| Digits & symbols | Unchanged | Shifted |
| Self-inverse | Yes | Yes |
| Typical use | Hiding spoilers and puzzle answers | Obscuring codes, emails, numbers |
Breaking a Caesar cipher
- Brute force: try all 25 shifts (use the "Show all 25 shifts" option).
- Frequency analysis: in English, the most common letter is usually E. If the most frequent ciphertext letter is H, the shift is probably 3.
Related tools
Try other codes with the Morse Code Translator or Upside Down Text, or encode data with Base64.
How to use the Caesar Cipher & ROT13
- Type or paste your text into the input box.
- Choose the options you want.
- The result updates instantly as you type.
- Copy the output or download it as a .txt file.