ROT18 Encoder and Decoder

Apply ROT13 to ASCII letters and ROT5 to ASCII digits in one fixed, self-inverse transformation.

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

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

ASCII letters use ROT13 and ASCII digits use ROT5. Every other character is preserved.

Apply ROT18 again to recover the original text.

What this tool does

Transform uppercase and lowercase ASCII letters by 13 positions and ASCII digits by 5 positions.

Use the same operation to encode or decode because both component rotations are self-inverse.

How to use the tool

  1. Type or paste mixed text into the input field.
  2. Read the ROT18 result as it updates automatically.
  3. Copy the result when needed.
  4. Apply ROT18 to the result again to restore the original text.

Useful applications

  • Read or create legacy ROT18 text containing letters and numbers.
  • Check ROT18 examples in software tests or technical documentation.
  • Demonstrate the combination of ROT13 and ROT5 in lessons.
  • Transform identifiers or sample strings while preserving punctuation.

Notes and limitations

  • ROT18 changes only ASCII letters A–Z and a–z plus digits 0–9.
  • Letters keep their case; punctuation, spaces, accented letters and other scripts remain unchanged.
  • ROT18 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?

ROT13 on a 26-letter alphabet and ROT5 on ten digits both reverse themselves when applied twice.

How does ROT18 differ from ROT13?

ROT18 additionally rotates ASCII digits 0–9 by five positions.

Does ROT18 change punctuation or accented letters?

No. This implementation changes only ASCII letters and ASCII digits.

Can ROT18 protect passwords or confidential data?

No. Anyone can reverse it immediately by applying ROT18 again.

Is my text uploaded?

No. The transformation runs locally in your browser.

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