Caesar Cipher Encoder and Decoder
Encrypt and decrypt text with the Caesar cipher, choose a shift from 1 to 25, or brute force every shift at once. Free, instant and runs entirely in your browser.
How to use Caesar Cipher
- 1Type or paste your text and choose Encrypt or Decrypt.
- 2Set the shift from 1 to 25 with the number box or the slider, and pick the alphabet.
- 3Copy the result, or switch the view to Brute force to see every shift side by side and copy the readable line.
What makes it better
- Encrypt and decrypt with any shift from 1 to 25, updated as you type
- Brute-force view lists all 25 shifts so a message with an unknown key can be read
- Keeps capitals, spaces, digits, punctuation and emoji, or outputs plain upper-case letters
- English A–Z or your own custom alphabet for other languages
About Caesar Cipher
The Caesar cipher replaces every letter with the one a fixed number of places further along the alphabet, so with a shift of 3 an A becomes a D. This tool encrypts and decrypts live as you type, keeps your capitals and punctuation if you like, and has a brute-force view that lists all 25 possible shifts so you can spot the readable one. It runs in your browser, so nothing you type is sent anywhere.
Common uses
- Solve a Caesar-style clue in a puzzle, escape room, geocache or CTF warm-up.
- Show a class why a cipher with only 25 keys is trivial to break.
- Make a quick spoiler-hiding code for a forum post or a game.
- Check a homework answer when learning about substitution ciphers.
Example
Input
Hello, World!
Result
Khoor, Zruog!
Good to know
- Classical ciphers offer no real security: a computer breaks them in milliseconds. For real encryption use AES-256 (see AES Encrypt).
- Only letters in the chosen alphabet are shifted. Digits, punctuation and accented letters outside it are left as they are unless you turn off the keep-everything option, which drops them.
- ROT13 is simply a Caesar cipher with shift 13. It has its own page because applying it twice returns the original text.
Caesar Cipher FAQ
What is the Caesar cipher?
It is one of the oldest ciphers, said to have been used by Julius Caesar. Each letter is moved a fixed number of positions along the alphabet and wraps from Z back to A. The shift is the secret key.
How do I decrypt a Caesar cipher without knowing the shift?
Open the Brute force view. It decrypts the text with every shift from 1 to 25 and lists them together, and one line will read as normal words. Short messages can have more than one plausible line, so read a few.
Is the Caesar cipher secure?
No. There are only 25 usable keys, and letter-frequency analysis also breaks it. It is fine for puzzles and teaching, never for protecting real data. Use AES for that.
Why does shifting by 26 change nothing?
The English alphabet has 26 letters, so 26 steps lands back on the starting letter. That is why only shifts 1 to 25 are useful, and why decrypting by 3 is the same as encrypting by 23.
Can I use it for languages other than English?
Yes. Choose the custom alphabet and enter your letters in order, for example the Cyrillic or Spanish alphabet. Letters outside it pass through unchanged, and the brute force view adjusts to the alphabet length.