Caesar Cipher
Encode and decode text with a Caesar shift cipher. Choose any shift from 1 to 25.
The Caesar cipher shifts each letter by a fixed number of places — the classic cipher said to be used by Julius Caesar. Caesar Cipher lets you encode and decode text with any shift from 1 to 25, for puzzles, teaching and lightweight obscuring.
How to use caesar cipher
- 1. Paste your text.
- 2. Choose a shift amount (1–25) and encode or decode.
- 3. Copy the result.
When to use Caesar Cipher
Puzzles and games
Create or crack a shifted-cipher message.
Teach cryptography basics
Demonstrate how a substitution cipher works with an adjustable shift.
Casual obscuring
Scramble text so it isn't readable without knowing the shift.
How the shift works
Each English letter moves forward in the alphabet by the shift you choose, wrapping from Z back to A; capitals stay capitals. With a shift of 3, "abc" becomes "def". Digits, punctuation and accented letters are left as they are. Decode uses the same shift in the opposite direction.
Breaking one without the key
There are only 25 possible shifts, so a message can be cracked by trying them all: paste it, press Decode, and change the shift until the text becomes readable. A shift of 13 is ROT13.
Frequently asked questions
How do I decode a Caesar message?
Apply the opposite shift, or decode with the same shift used to encode. ROT13 is just a Caesar cipher with a shift of 13.
Is it secure?
No — with only 25 possible shifts it's trivial to break. Use it for fun and learning, not protection.
Is my text private?
Yes — it's processed in your browser.