ROT13, Caesar, and Atbash Cipher Tool
Encode and decode text with three classic ciphers: ROT13, the general Caesar shift, and Atbash. It is a fast way to explore classical cryptography or obscure spoilers in plain sight.
How to use the ROT13 & Caesar Cipher
- Type or paste the text you want to transform.
- Choose a cipher: ROT13, a Caesar shift with your chosen offset, or Atbash.
- The result appears immediately, and running the same cipher again reverses it.
- Copy the encoded or decoded output as needed.
When the ROT13 & Caesar Cipher is useful
- Obscuring spoilers or puzzle answers in forums.
- Solving newspaper cryptograms and puzzle-hunt challenges.
- Teaching the history of ciphers in classrooms and workshops.
- Creating themed game content with hidden messages.
How the ROT13 & Caesar Cipher works
ROT13 shifts every letter thirteen positions, which makes it its own inverse. The Caesar mode lets you pick any shift from one to twenty-five, matching the original cipher Julius Caesar reportedly used with a shift of three. Atbash mirrors the alphabet, swapping the first letter for the last and so on. All three preserve character case and leave non-letters untouched, and all run locally in your browser.
Limits to keep in mind
These ciphers are historical toys, not security; never use them to protect genuinely sensitive information.
Frequently asked questions
Why does ROT13 decode with the same operation?
Because thirteen is exactly half the alphabet, applying the shift twice returns the original letter.
What shift did Caesar actually use?
Historical accounts describe a shift of three, which you can reproduce in Caesar mode.
Are numbers and punctuation changed?
No, only alphabetic characters are shifted; everything else passes through unchanged.
Last reviewed: October 2026.