Is ROT13 a form of encryption?

ROT13 is a cipher but not a secure encryption method. It provides no cryptographic protection — anyone who recognizes the pattern can decode it immediately. It is best used for casual obfuscation, not security.

Why does applying ROT13 twice restore the original text?

The English alphabet has 26 letters. Shifting by 13 twice gives a total shift of 26, which is a full cycle, so every letter returns to its starting position.

What happens to numbers and punctuation?

Numbers, spaces, punctuation, and all non-letter characters are passed through unchanged. Only the 26 letters of the Latin alphabet (A–Z, a–z) are affected.

Is ROT13 the same as Caesar cipher?

ROT13 is a special case of the Caesar cipher with a fixed shift of 13. A general Caesar cipher allows any shift from 1 to 25, while ROT13 always uses 13.

Does this tool send my text to a server?

No. All processing happens entirely in your browser using JavaScript. Your text never leaves your device.

Can I use ROT13 on non-English text?

ROT13 only affects the 26 standard Latin letters (A–Z). Accented characters, Cyrillic, CJK, and other scripts are passed through unchanged.

ROT13 Cipher

Type or paste text to instantly encode or decode it with ROT13 — the same operation works both ways.

Input Text

Characters

Words

Letters shifted

ROT13 Output

Apply again to decode

Alphabet Mapping

Plain
ROT13

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Summary

ROT13 is a simple letter-substitution cipher that shifts each letter 13 positions forward in the alphabet. Because the alphabet has 26 letters, applying ROT13 twice returns the original text, making encoding and decoding identical operations. It is commonly used to obscure spoilers, joke punchlines, and puzzle answers in online communities.

How it works

Type or paste your text into the input field.
Each letter is shifted 13 positions forward in the alphabet (A becomes N, B becomes O, etc.).
Uppercase letters map to uppercase, lowercase to lowercase.
Numbers, spaces, and all other characters pass through unchanged.
The result appears instantly in the output field — apply it again to decode.
Use the Copy button to copy the result to your clipboard.

Use cases

Hide spoilers in forums and comment sections without a spoiler tag.
Obfuscate puzzle answers so readers can choose whether to reveal them.
Decode ROT13-encoded text found in Usenet posts, Reddit comments, or old forums.
Teach introductory cryptography concepts — ROT13 is the simplest Caesar cipher.
Quickly scramble text for lightweight obfuscation in emails or messages.
Verify ROT13 implementations during software testing.
Encode punchlines in trivia games so they are not immediately visible.
Process code strings that use ROT13 as a basic obfuscation layer.

Frequently Asked Questions

Last updated: 2026-05-23 · Reviewed by Nham Vu