DocomintCaesar Cipher / ROT13 Encoder
Encrypt or decrypt text with a classic Caesar cipher, including the ROT13 preset.
A Caesar cipher shifts every letter forward in the alphabet by a fixed amount and wraps around at the end — ROT13 is just the special case where that shift is 13, which also happens to be self-reversing (running it twice returns the original text).
Example: With a shift of 3, "attack at dawn" becomes "dwwdfn dw gdzq" — a classic example of the cipher Julius Caesar is said to have used for military messages.
How it works
- Type your message
- Pick a shift amount (13 = ROT13) and encrypt or decrypt
- The shifted text appears instantly, on your device
Frequently asked questions
Is a Caesar cipher secure?
No — it's a classical cipher with only 25 possible shifts, easily broken by hand or by trying every shift. Use it for puzzles or teaching, not for protecting real secrets.
Is my text uploaded anywhere?
No — Caesar Cipher / ROT13 Encoder runs entirely in your browser using JavaScript/WebAssembly. Your text is never sent to a server.
What shift amount should I use if I'm not specifically going for ROT13?
Any number from 1-25 works — 13 (ROT13) is popular purely because it's self-reversing, but the cipher itself offers no real security at any shift, since there are only 25 possible shifts to try.