ROT13 Cipher
Free online ROT13 cipher encoder. Shift letters by 13 positions. Same tool encodes and decodes — ROT13 is its own inverse. Numbers and punctuation pass through unchanged.
How to Use ROT13 Cipher
Enter Your Text
Type or paste any text into the input area. ROT13 works on letters only — numbers, spaces, and punctuation pass through unchanged.
Click Convert
Click "ROT13 Encode/Decode" to shift each letter by 13 positions in the alphabet. Since ROT13 is its own inverse, the same button both encodes and decodes.
Copy the Result
Copy the output text. Apply ROT13 again to the result and you'll get back the original text — that's the beauty of the ROT13 cipher.
Examples
Original
Hello, World!ROT13
Uryyb, Jbeyq!Frequently Asked Questions
What is ROT13?
ROT13 ("rotate by 13 places") is a Caesar cipher that shifts each letter 13 positions forward in the alphabet. A becomes N, B becomes O, and so on. Because the English alphabet has 26 letters, applying ROT13 twice returns the original text — it's its own inverse. ROT13 is NOT encryption and provides zero security; it's used mainly for hiding spoilers, puzzle answers, and offensive content on forums.
Why 13 positions?
13 is exactly half of 26 (the number of letters in the English alphabet), which makes ROT13 self-inverse. The same code can both encode and decode — no need for a separate "decode" function. This makes it trivially simple to implement and use. ROT5 (for digits) and ROT47 (for printable ASCII) follow similar principles but with different character ranges.
Is ROT13 case-sensitive?
Yes, this converter preserves case. Uppercase letters map to uppercase (A→N, N→A), and lowercase letters map to lowercase (a→n, n→a). Non-letter characters (numbers, spaces, punctuation, symbols, emoji) pass through unchanged. This preserves the readability of the original text structure.
ROT13 and the Caesar Cipher Family
ROT13 is the most famous member of the Caesar cipher family, named after Julius Caesar who used ROT3 for military communications. While Caesar ciphers have zero security value today (they can be broken by hand in seconds), ROT13 found a niche on the early internet as a quick way to hide content that readers might not want to see — spoilers, puzzle solutions, punchlines, and offensive material.
ROT Variants
- ROT5 — Shifts digits 0-9 by 5 positions (0↔5, 1↔6, etc.). Self-inverse like ROT13.
- ROT13 — Shifts A-Z/a-z by 13. The most common variant.
- ROT18 — ROT13 for letters + ROT5 for digits. Used in some Usenet communities.
- ROT47 — Shifts all printable ASCII characters (33-126) by 47 positions. More thorough obfuscation.