ROT13 converter

Encode/decode text with ROT13.

ROT13 encoding equals decoding (same operation). Only letters change; numbers, Korean, and symbols stay as-is.

You want to post the answer to a riddle in a forum thread without spoiling it for the next reader, so you scramble it and let anyone who wants the answer unscramble it.

ROT13 is the classic way to do that. It rotates each letter thirteen places through the alphabet, turning readable text into something no one can accidentally read - while staying trivial to reverse for anyone who wants to. Paste text in, press Convert, and the transformed version appears below.

How it works

Shifting by thirteen

Each letter moves thirteen positions forward through the alphabet, wrapping around from Z back to A. So A becomes N, B becomes O, and M becomes Z. Hello becomes Uryyb.

Why one button does both jobs

The English alphabet has 26 letters, and 13 is exactly half of that. Shift a letter thirteen places and then thirteen more and you have moved a full 26 - back to where you started. ROT13 is therefore its own inverse: there is no separate decode mode, because running the conversion a second time restores the original text. That is why the input box says applying ROT13 again gives you what you started with.

What stays the same

Only the 26 basic Latin letters are affected, and case is preserved - uppercase stays uppercase, lowercase stays lowercase.

Changed: A-Z and a-z
Unchanged: digits, spaces, punctuation, symbols, line breaks
Unchanged: accented letters and non-Latin scripts such as Korean, Japanese or Cyrillic

Because numbers survive intact, a string like Room 305 becomes Ebbz 305 - the digits still give part of it away. Some variants (often called ROT18 or ROT5) also rotate digits; this tool does not.

One important limit

ROT13 is not encryption and offers no security whatsoever. There is no key, the method is public, and any solver breaks it instantly. Its whole purpose is to prevent accidental reading - spoilers, puzzle answers, punchlines. Never use it for passwords, personal details, or anything that would matter if a stranger read it.

Terms explained

ROT13: A substitution cipher that rotates each letter 13 places through the alphabet. The name is short for rotate by 13.
Caesar cipher: The general family ROT13 belongs to, where every letter shifts by a fixed number of positions. ROT13 is the special case where that number is 13.
Self-inverse: A property of an operation that undoes itself when applied twice. Because 13 + 13 = 26, one full alphabet, ROT13 is self-inverse.
Substitution cipher: A scheme that replaces each character with another according to a fixed rule. Easily broken by frequency analysis, so it is not used for real security.
ROT47: A related scheme that rotates 94 printable ASCII characters by 47 places, so digits and punctuation are scrambled too - unlike ROT13, which leaves them alone.

Frequently asked questions

Is ROT13 secure enough to hide sensitive information?

No, and it is not intended to be. There is no key and the method is completely public, so anyone who recognises the text can reverse it in seconds. Use it only for things like spoilers and puzzle answers, where the goal is preventing accidental reading rather than protecting a secret.

Why is there no decode button?

Because encoding and decoding are the same operation. Thirteen is half of the 26-letter alphabet, so applying the shift twice moves each letter a full lap and returns it to its starting point. Just run your encoded text through Convert again to read it.

Why did my numbers and punctuation stay the same?

ROT13 is defined only over the 26 basic Latin letters, so digits, spaces, symbols and line breaks pass through untouched. That means a date or a room number in your text remains readable. If you need digits scrambled too, look for a ROT47 or ROT5 variant rather than plain ROT13.

Does it work with non-English text?

Only the parts written in basic Latin letters are transformed. Accented characters such as e-acute or umlauts, and any non-Latin script such as Korean, Cyrillic or Japanese, are left exactly as they are - so text in those scripts comes back essentially unchanged.

Where is ROT13 actually used?

It has been a convention on discussion forums and Usenet for decades as a way to mark spoilers, joke punchlines and puzzle solutions - readers who want the answer decode it, and everyone else scrolls past. It also turns up as a light obfuscation step in programming exercises and puzzle games.