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Kordu Tools
Classical Ciphers Runs in browser Updated 02 Apr 2026

ROT13 Encoder

Encode text with ROT13 or ROT47 instantly. ROT13 is self-inverting — encoding and decoding are the same operation. Used for spoilers and puzzle forums.

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How to use ROT13 Encoder

  1. Type or paste your text

    Enter the plain text you want to encode in the input panel. The ROT13 output updates in real time as you type.

  2. Choose ROT13 or ROT47

    ROT13 rotates letters only (A–Z, a–z). ROT47 also rotates digits and printable punctuation (ASCII 33–126). Select the variant that fits your use case.

  3. Copy the encoded output

    Click Copy to copy the encoded text to your clipboard. To decode, paste the output back into the encoder — the result is identical to the original text.

ROT13 Encoder FAQ

What is ROT13?
ROT13 (Rotate by 13) is a substitution cipher that shifts each letter 13 positions forward in the alphabet. A becomes N, B becomes O, N becomes A, and so on. Non-letter characters are unchanged. Because the English alphabet has 26 letters, applying ROT13 twice returns the original text.

Is encoding the same as decoding in ROT13?
Yes. ROT13 is its own inverse: ROT13(ROT13(text)) = text. The same operation both encodes and decodes. Paste encoded ROT13 into this tool and you get the original text back.

Is this tool safe? Are inputs sent to a server?
No data is uploaded. All encoding happens in your browser using JavaScript. Your text never leaves your device.

What is ROT47 and how is it different from ROT13?
ROT47 rotates all 94 printable ASCII characters (code points 33–126, which includes digits, punctuation, and letters) by 47 positions. ROT13 only rotates the 26 Latin letters. Both are self-inverting. Use ROT47 when you want to also encode digits and symbols.

Is ROT13 secure for sensitive data?
No. ROT13 is trivially reversible and provides no cryptographic security. Use it only for casual obfuscation (spoilers, puzzle hints) — never for passwords, tokens, or private data. For actual encryption, use AES-256-GCM.

What characters are left unchanged by ROT13?
All non-letter characters — digits, punctuation, spaces, and emoji — pass through unchanged. ROT47 also leaves spaces and characters outside ASCII 33–126 unchanged.

Where is ROT13 used?
ROT13 has been the traditional spoiler convention on Usenet since the 1980s. It is used on Reddit, gaming forums, and puzzle communities to hide answers without a password. Its symmetry makes it convenient — any Morse ROT13 tool decodes as well as encodes.

What does ROT13 of ROT13 equal?
The original text. Because ROT13 shifts by exactly half the alphabet, applying it twice returns every letter to its starting position. ROT13(ROT13('HELLO')) = 'HELLO'.

Can I use ROT13 to hide passwords?
No. ROT13 is well-known and trivially reversible. Never use it for passwords, API keys, or any security-sensitive data. Use a password manager and proper encryption (AES-256) for sensitive information.

Background

Encode text with ROT13 or ROT47 in real time, entirely in your browser.

ROT13 rotates each letter 13 positions in the alphabet. Uppercase and lowercase letters are handled independently; numbers, punctuation, and spaces are left unchanged. Because 13 + 13 = 26 (the full alphabet length), ROT13 is its own inverse — the same operation both encodes and decodes.

ROT47 extends this to all 94 printable ASCII characters (code points 33–126), rotating each by 47 positions. ROT47 encodes digits and common punctuation in addition to letters — also self-inverting.

Common uses:

  • Hiding spoilers on Reddit, Usenet, and gaming forums
  • Obscuring puzzle answers without a password
  • CTF challenge obfuscation (often ROT47 for broader coverage)
  • Quick fun or educational demonstrations of substitution ciphers

ROT13 and ROT47 provide no cryptographic security. Use them only for casual text scrambling — never for sensitive data.

All processing runs entirely in your browser. Nothing is uploaded.

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