ROT13 Encoder/Decoder

Apply the ROT13 (or any ROT-N) letter-shift cipher to text. Same action encodes and decodes — perfect for spoilers, puzzles, and obfuscation.

About ROT13 Encoder/Decoder

Overview

The ROT13 Encoder/Decoder rotates every letter in your text by a fixed number of positions in the alphabet. The classic ROT13 uses a shift of 13, which is special: applying it twice returns the original text, so the same action both encodes and decodes. Only the letters A–Z and a–z are rotated; numbers, spaces, punctuation, and accented characters are left exactly as they are.

Features

  • Classic ROT13 by default, plus any ROT-N shift from 1 to 25.
  • Same action encodes and decodes — the cipher is its own inverse.
  • Only rotates the letters A–Z and a–z; numbers, spaces, and punctuation are left untouched.
  • Live mode updates the output instantly as you type.
  • Optional Swap button moves the output back into the input for quick round-trips.
  • One-click copy to clipboard.
  • Supports file uploads up to 100MB through the input box.
  • All processing happens in your browser — your text is never sent anywhere.
  • Dark mode and a clean, mobile-friendly layout.

How to Use

  1. Type or paste your text into the input box, or drag & drop a text file.
  2. Pick a rotation value from 1 to 25. The default of 13 is the classic ROT13.
  3. Leave Live Mode on to see the result update as you type, or turn it off and use the APPLY ROTATION button instead.
  4. The transformed text appears in the output box. Only letters change; everything else stays the same.
  5. Click "Copy" to put the result on your clipboard, or use "Swap Input/Output" to feed the output back in as new input.
  6. Use the "Clear" button to start over.

FAQ

What is ROT13?

ROT13 is a simple letter-shift cipher that rotates every letter by 13 positions in the alphabet. Because the Latin alphabet has 26 letters, applying ROT13 a second time returns the original text. It is widely used to hide spoilers, puzzle answers, and off-color jokes in plain sight on the web.

Does this tool encrypt my text?

No. ROT13 is an obfuscation, not encryption. Anyone who knows the trick can read the message in seconds. Use a real encryption tool for anything that needs to stay secret.

Why are numbers and punctuation left unchanged?

ROT13 is defined only for the letters A–Z and a–z. Numbers, spaces, punctuation, and accented or non-Latin characters have no fixed position in the rotation, so the tool leaves them alone to keep your formatting, code, and line breaks intact.

Can I use a shift other than 13?

Yes. The rotation slider goes from 1 to 25, so you can use any classic Caesar shift. Pick a value, type your text, and the same APPLY ROTATION action works for any choice.