ROT13 Cipher

What this tool does

The ROT13 tool takes any text you type or paste and rotates every letter 13 positions through the alphabet. A becomes N, B becomes O, C becomes P, and so on until N wraps around to A. Case is preserved: uppercase letters become uppercase, lowercase stay lowercase. Digits, spaces and all punctuation marks pass through completely unchanged. The result appears in the output box as you type — there is no button to press.

What makes ROT13 unusual is that it is its own inverse. The Latin alphabet has 26 letters and 13 is exactly half of 26, so rotating by 13 twice always brings a letter back to its starting point. That means you do not need separate encode and decode modes: paste the original text and get the ROT13 version; paste the ROT13 version and get back the original. A single pass does both.

Why you might need it

ROT13 has been a staple of internet culture since the Usenet era of the 1980s. Its most common use is hiding spoilers — a film reveal, the answer to a riddle, the punchline of a joke — so that readers can choose whether to decode them. Forums dedicated to books, games and puzzle-solving still use it for exactly this purpose.

Developers encounter ROT13 as a running joke embedded in software Easter eggs, and it occasionally appears in beginner cryptography lessons as the simplest possible example of a substitution cipher. It is also useful in word puzzles and simple games where you want to obscure text just enough that a casual glance will not immediately reveal the answer.

If you simply need to check whether a string you received is ROT13-encoded, paste it here and the decoded version appears instantly. No account, no upload, no waiting.

How to use it

1. Type or paste your text into the Input text box.
2. The ROT13 output appears in the lower box immediately — every keystroke updates the result in real time.
3. To decode ROT13 text back to the original, paste the encoded string into the same input box. The output will be the plain text.
4. Click Copy output to copy the result to your clipboard.
5. Use Load sample to see a quick demonstration, or Clear to start over.

Common pitfalls

The most frequent point of confusion is expecting ROT13 to handle non-Latin alphabets. It only rotates the 26 letters A–Z. Accented characters like é, ü or ñ pass through unchanged, so text in French, German or Spanish will have those letters left as-is while the basic Latin letters rotate normally. Similarly, digits and punctuation are never touched.

A second surprise: because the same operation encodes and decodes, if you paste already-ROT13’d text and then click “Load sample”, the sample overwrites your input. Make sure to copy the output first before loading a new sample.

Do not rely on ROT13 for anything confidential. It offers no security whatsoever. Any reader who suspects ROT13 — which is most technically inclined people — can decode it in seconds with this or any other tool. It is purely a novelty.

Tips and advanced use

ROT13 is a subset of the Caesar cipher family. If you need a different rotation amount — say, shift 5 or shift 21 — see the Caesar Cipher tool, which lets you pick any shift from 1 to 25.

For puzzle design, ROT13 is particularly handy because the encoded text looks plausibly like words — many common English letter combinations ROT13 to other common combinations — which makes the output look less obviously scrambled than, say, a random substitution. That mild plausibility is part of what gives it its puzzle-spoiler charm.

Because everything runs in your browser, there is no risk in pasting unpublished or internal text here. Nothing leaves your device.