ROT13 & Caesar Cipher
Encode and decode text with ROT13 or a Caesar shift.
Pick a shift from 0 to 25, encode or decode, live as you type.
Your Result
What are ROT13 and the Caesar cipher?
ROT13 and the Caesar cipher are simple letter-shift ciphers. Each letter is moved a fixed number of places along the alphabet, wrapping around from Z back to A, so the message turns into a scramble that you reverse with the same shift. Type or paste your text above, choose ROT13 or a Caesar shift, and the result appears instantly, ready to copy or download. It runs entirely in your browser, so nothing you type leaves your device.
A letter shift works one letter at a time. With a shift of 3, A becomes D, B becomes E, and at the end of the alphabet the count wraps around, so X becomes A, Y becomes B and Z becomes C. The Caesar cipher is named after Julius Caesar, who is said to have used a shift of three. ROT13 is just a Caesar cipher with a shift of 13, and because 13 is half of 26 it is its own inverse: running ROT13 on already-scrambled text gives back the original, so the same step both hides and reveals.
Only the 26 basic English letters are shifted, and case is preserved, so an uppercase letter stays uppercase. Numbers, spaces, punctuation and any accented or non-English letters pass through untouched, which keeps the shape of the text the same and changes only the plain A to Z letters. Under ROT13, for example, A becomes N and Hello becomes Uryyb.
These ciphers are great for hiding spoilers, sharing puzzle answers, light wordplay and learning how ciphers work. One thing they are not is secure: with only 26 possible shifts and no real key, a Caesar cipher can be broken in seconds, so never use it to protect anything sensitive. To use the tool, type your text, pick ROT13 or a Caesar shift from 0 to 25, and switch between Encode and Decode. It sits beside the other transforms: the binary translator turns text into binary, the reverse text generator flips text, and the word counter counts your writing. Everything runs in your browser with no account and nothing to install. Enter text above to encode or decode it instantly.
ROT13 & Caesar Cipher Examples
| Cipher | Input | Result |
|---|---|---|
| ROT13 | Hello, World! | Uryyb, Jbeyq! |
| ROT13 again (decodes) | Uryyb, Jbeyq! | Hello, World! |
| Caesar shift 3 | abc xyz | def abc |
| Caesar shift 3 (decode) | def abc | abc xyz |
| A under ROT13 | A | N |
*Every row is produced by the same engine this page uses. The input column is the real text; the result column is what the tool returns.
Features of Our ROT13 & Caesar Cipher Tool
Caesar Shift
Decode
0 to 25
& Symbols
You Type
Download
& Private
Frequently Asked Questions
Click any question to read the answer.
What is ROT13?
ROT13 is a simple letter cipher that rotates each letter 13 places through the alphabet, so A becomes N, B becomes O, and so on. Because 13 is exactly half of 26, applying ROT13 a second time brings you back to the original text, which means the same operation both hides and reveals the message. It is most often used online to hide spoilers, puzzle answers and punchlines behind a quick, reversible scramble.
What is a Caesar cipher?
A Caesar cipher shifts every letter a fixed number of places along the alphabet, wrapping around from Z back to A. It is named after Julius Caesar, who is said to have used a shift of three to protect his messages. ROT13 is simply a Caesar cipher with a shift of 13. With this tool you can choose any shift from 0 to 25 and encode or decode with it.
How do I decode ROT13?
Run the text through ROT13 again. Since ROT13 is its own inverse, encoding and decoding are the same step, so you do not need a separate decode mode for it. Paste the scrambled text with ROT13 selected and the readable version appears. For a Caesar shift, decoding means shifting back by the same amount, which the Decode option does for you.
Is ROT13 secure encryption?
No. ROT13 and the Caesar cipher are not secure and should never be used to protect anything sensitive. There are only 26 possible shifts, so anyone can break a Caesar cipher in seconds by trying them all, and ROT13 has no key at all. Treat these as fun, reversible scrambles for puzzles, spoilers and learning, not as real encryption.
How do I choose a Caesar shift?
Any shift from 1 to 25 works; a shift of 0 (or 26) leaves the text unchanged. To decode a message someone sent you, use the same shift they used, in the Decode direction. If you do not know the shift, you can try each one until the text reads sensibly, since there are only 25 to check. The classic Caesar shift is 3, and ROT13 uses 13.
Does the cipher change numbers and punctuation?
No. Only the 26 basic English letters, A to Z and a to z, are shifted. Digits, spaces, punctuation and symbols pass through unchanged, so the shape of the text stays the same and only the letters are scrambled. Letter case is preserved too, so an uppercase letter stays uppercase after the shift.
What happens to accented or non-English letters?
They are left untouched. The classic ciphers work on the 26-letter English alphabet only, so accented letters like é and characters from other scripts pass straight through without being shifted. If your text mixes English and other letters, only the plain A to Z letters change.
Is my text stored when I use this tool?
No. The cipher runs entirely as JavaScript inside your browser, so what you type is never uploaded, logged, or sent to a server. The page keeps working offline once it has loaded, and nothing leaves your device. You can scramble or unscramble private text with no privacy risk at all.