ROT13 rotates A–Z and a–z by 13 places. Applying it twice returns the original text.
ROT13 rotates A–Z and a–z by 13 places. Applying it twice returns the original text.
ROT13 / Caesar Cipher
Apply classic ROT13 (rotate letters by 13, its own inverse) or a Caesar cipher with any shift from 1 to 25. Choose encrypt or decrypt for Caesar, use presets or a slider, and keep numbers, punctuation, and Unicode outside basic Latin untouched. Large inputs run in a Web Worker; everything stays in your browser.
ROT13 / Caesar Cipher Use Cases
- Hide puzzle or story spoilers in forums and chats with reversible ROT13 text
- Teach classical substitution ciphers and modular arithmetic on the alphabet
- Quickly try several Caesar shifts when solving CTF or pen-and-paper riddles
- Normalize ROT13-encoded payloads from APIs or logs back to readable prose
ROT13 / Caesar Cipher FAQ
Is my text uploaded anywhere?
No. The transformation runs entirely in your browser. Your text never leaves your device.
Which characters are changed?
Only basic Latin letters A–Z and a–z are rotated. Spaces, digits, punctuation, accented letters, emoji, and all other Unicode code points are left unchanged.
Is this real encryption?
No. ROT13 and Caesar ciphers are obfuscation for fun, spoilers, or teaching — they are trivial to break and must not be used to protect secrets.
Why does large input use a Web Worker?
Inputs over 500KB are processed off the main thread so the editor stays responsive while every character is scanned.