Caesar Cipher Encoder & Decoder
Encrypt or decrypt text with a Caesar shift from 0 to 25. The output updates as you type.
Input
Caesar · shift 3 · encode
EncodedType text in the input panel to shift it.
The Caesar cipher shifts each letter a fixed number of places along the alphabet, wrapping past Z. With only 25 possible shifts it offers no real security — it's a teaching example and a puzzle staple. ROT13 (shift 13) is its own inverse, so the same operation hides and reveals text.
- Shifts
- 0–25
- Charset
- A–Z a–z
Related tools
The Caesar cipher swaps each letter for the one a fixed number of places further along the alphabet. With a shift of 3, A becomes D and HELLO becomes KHOOR. According to the Roman historian Suetonius, Julius Caesar used exactly that shift in his letters, which is how it got its name.
This Caesar cipher encoder and decoder shifts A–Z and a–z and keeps upper and lower case as they were. Digits, spaces, punctuation and accented letters pass through untouched. Choose a shift, choose Encode or Decode, and type. Set the shift to 13 and you have ROT13.
It's good for puzzles, classroom exercises and escape-room clues. It's useless for real secrets, since there are only 25 shifts to try.
What is a Caesar cipher?
A substitution cipher where every letter moves by the same amount, wrapping from Z back to A. With shift 3, A → D, B → E and X → A. People use it for:
- Teaching the basics of cryptography
- Puzzle hunts and geocache clues
- Coding exercises on strings and modular arithmetic
- Hiding spoilers with ROT13
How to use the Caesar cipher tool
- Type or paste your text into the input.
- Set the shift with the slider, from 0 to 25. It starts at 3.
- Choose Encode to shift forward or Decode to shift back.
- Click Copy result to copy the output.
Example outputs
The same idea with a few different shifts:
- HELLO, shift 3 → KHOOR
- WORLD, shift 2 → YQTNF
- Hello, World!, shift 13 → Uryyb, Jbeyq!
Frequently asked questions
Can I decode Caesar cipher text if I don't know the shift?
The tool won't guess it for you, but there are only 25 options. Switch to Decode and drag the slider until the output reads like words.
Is the Caesar cipher secure?
No. With 25 possible shifts it can be broken by hand in minutes. Use it for learning and games, not for anything private.
What happens to numbers and punctuation?
They're left alone. Only the 26 letters of the English alphabet are shifted, in both upper and lower case.
Why do Encode and Decode give the same result at shift 13?
Because 13 is half of 26. Shifting by 13 twice brings every letter back to where it started, so ROT13 undoes itself.
Is this Caesar cipher tool free?
Yes, with no sign-up. The shifting happens in your browser.
Built and maintained by Bipul Kumar. Found a wrong number or a broken result? Tell me and I'll fix it.