Caesar Cipher
Shift letters by any amount to encode or decode a message.
The classic shift cipher
Named for Julius Caesar, this cipher shifts every letter a fixed number of places down the alphabet. It is the simplest substitution cipher and a great introduction to how encryption works.
With a shift of 3, HELLO becomes KHOOR. Non-letters pass through unchanged and case is preserved. To decode, use the same shift in decode mode and the original text returns.
For learning, not secrecy
Everything runs in your browser, so your text is never uploaded — though a Caesar cipher offers no real security.
Frequently Asked Questions
What is a Caesar cipher?
A substitution cipher that shifts each letter a fixed number of places along the alphabet. A shift of 3 turns A into D.
How do I decode?
Switch to decode mode with the same shift, or the tool reverses the shift for you.
Is it secure?
No. With only 25 possible shifts it is trivial to break, so it is for learning and puzzles, not real secrecy.
Browse the full set of free, private, in-browser tools.