Caesar Cipher / ROT13
Encode or decode text with a Caesar cipher (including the classic ROT13 shift), with any shift amount from 1 to 25 — instantly, in your browser.
A Caesar cipher shifts every letter in your text by a fixed number of positions in the alphabet — the classic ROT13 (shift 13) is the most common variant. Enter your text and a shift amount below, entirely in your browser.
How it works
Every letter is shifted forward (encode) or backward (decode) by your chosen amount, wrapping around the alphabet (Z shifted by 1 becomes A). Case is preserved; numbers, spaces, and punctuation are left untouched.
This is not real encryption. A Caesar cipher has only 25 possible shifts, so it can be broken instantly by trying all of them — it’s included here as a classic educational and puzzle tool, not a way to protect sensitive information.
FAQs
What is ROT13?
ROT13 is a Caesar cipher with a shift of exactly 13 — historically popular online because applying it twice returns the original text, making it a convenient (not secure) way to obscure spoilers or puzzle answers.
Should I use this to protect private information?
No. Use a real encryption tool for that. A Caesar cipher can be decoded by anyone in seconds, with or without knowing the shift amount.