ROT13 / Caesar Cipher
Encode and decode text with a Caesar shift cipher.
🔒 100% private — your files are processed locally and never leave your device.
One of the oldest encryption methods in history simply shifts each letter a fixed number of places along the alphabet. The ROT13 / Caesar Cipher tool applies that classic shift to your text — with ROT13 (a shift of 13) as the popular default — to lightly scramble a message or reveal one that has been scrambled.
How to use the ROT13 / Caesar tool
- Paste your text.
- Choose a shift amount (13 is the ROT13 default).
- Click Apply to encode or decode.
- Copy the result.
An ancient cipher with modern uses
Named after Julius Caesar, who used it to protect military messages, the shift cipher is trivial to break today and offers no real security — but that is exactly why it survives as a friendly tool rather than a serious one. ROT13 in particular is widely used online to hide spoilers, punchlines and puzzle answers in plain sight: applying ROT13 twice returns the original text, so the same button both hides and reveals. It is also a perfect first lesson in how ciphers work.
Tips for the cipher
- ROT13 is its own inverse; apply it again to decode.
- For other shifts, decode with the opposite shift (or 26 minus your shift).
- Only letters move; numbers, spaces and punctuation stay put.
- Never use it for real secrets — it is for fun and learning.
The shift is applied in your browser, so your text never leaves your device.
Quick reference
| Property | Detail |
|---|---|
| Method | Letter shift (Caesar) |
| Default | ROT13 (shift 13) |
| Reversible | ROT13 is its own inverse |
| Affects | Letters only |
| Security | None — for fun/learning |