ROT13 Encoder and Decoder

Apply the fixed ROT13 transformation to uppercase and lowercase ASCII letters. The same operation encodes and decodes.

The conversion runs locally. Digits, punctuation, accented letters and non-Latin scripts stay unchanged.

The conversion runs locally. Digits, punctuation, accented letters and non-Latin scripts stay unchanged.

Only ASCII letters A–Z and a–z are rotated by 13 positions. Everything else is preserved.

Apply ROT13 again to recover the original text.

What this tool does

Transform ASCII letters by exactly 13 alphabet positions while preserving letter case.

Use the same operation to encode or decode because ROT13 is its own inverse.

How to use the tool

  1. Type or paste text into the input field.
  2. Read the ROT13 result as it updates automatically.
  3. Copy the result when needed.
  4. Apply ROT13 to the result again to restore the original text.

Useful applications

  • Reveal or hide lightweight spoiler text that uses ROT13.
  • Check ROT13 examples in software tests or documentation.
  • Demonstrate a self-inverse substitution cipher in lessons.
  • Transform mixed text while leaving numbers and punctuation untouched.

Notes and limitations

  • ROT13 changes only the ASCII letters A–Z and a–z.
  • Digits, spaces, punctuation, accented letters and other scripts remain unchanged.
  • ROT13 is an encoding convention, not encryption, and provides no confidentiality.
  • The text is processed in the browser and is not sent to petuja.tools by this tool.

Frequently asked questions

Why are encoding and decoding identical?

Rotating the 26-letter alphabet by 13 positions twice returns every letter to its starting position.

Does ROT13 change numbers or punctuation?

No. This implementation changes only uppercase and lowercase ASCII letters.

Are accented letters such as ä or é rotated?

No. They are outside the ASCII A–Z and a–z ranges and remain unchanged.

Can ROT13 protect confidential information?

No. Anyone can reverse it immediately by applying ROT13 again.

Is my text uploaded?

No. The transformation runs locally in your browser.

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