Caesar Cipher Encoder and Decoder
Encrypt and decrypt text with the Caesar cipher. Choose a shift from 0 to 25, or decode without the key and see all 25 shifts at once. Free, runs in your browser.
How it works
The Caesar cipher replaces every letter with the letter a fixed number of places further along the alphabet. Number the letters A = 0, B = 1 … Z = 25. To encrypt with a shift of 3, add 3 to each letter and wrap around after Z, so A becomes D and X becomes A. To decrypt, subtract the shift. Only the letters A to Z are changed and their upper or lower case is kept. Digits, spaces, punctuation, letters of other alphabets and emoji stay as they are. A shift of 0 leaves the text unchanged. In Decrypt mode the page also lists the result for every shift from 1 to 25, so you can find the readable line when the shift is not known. A shift of 13 is ROT13, where the same step both encrypts and decrypts.
Example: with a shift of 3, Veni, vidi, vici becomes Yhql, ylgl, ylfl, and HELLO becomes KHOOR. Decrypting KHOOR with a shift of 3 gives HELLO back.
Frequently asked questions
How do I encrypt text with the Caesar cipher?
Choose Encrypt, set a shift from 0 to 25 and paste your text. Every letter moves forward by that number of places. The result appears as you type and you can copy it with one click.
How do I decrypt a Caesar cipher if I know the shift?
Choose Decrypt and enter the same shift that was used to encrypt. Each letter moves back by that number of places.
How do I decode a Caesar cipher without knowing the shift?
Choose Decrypt and look at the list of all 25 shifts under the result. Only one of them is readable text, and that line shows the original message and its shift. There are just 25 possible shifts, so checking them all is quick.
What shift did Julius Caesar use?
A shift of 3 is the traditional example, and it is the default here: A becomes D, B becomes E and so on.
Is ROT13 the same as the Caesar cipher?
ROT13 is the Caesar cipher with a shift of 13. Because the English alphabet has 26 letters, applying a shift of 13 twice returns the original text.
What happens to numbers, spaces and punctuation?
They are copied unchanged. Only the letters A to Z are shifted. Letters with accents, such as é or ł, are left as they are.
Is the Caesar cipher secure?
No. With only 25 possible shifts it can be broken in moments, so use it for puzzles, learning and games, not for real secrets.
Is my text sent to a server?
The encryption runs in your browser and your text is not sent anywhere.
More text tools
- Morse Code Translator
- Binary Translator
- ASCII Converter
- Hex to Text Converter
- Leet Speak Translator
- Vigenere Cipher Encoder and Decoder
- Atbash Cipher Encoder and Decoder
- Word Counter and Character Counter
A classical cipher for puzzles and learning. It does not protect real secrets.