ROT13 Encoder
ROT13 Encoder replaces A–Z and a–z with the letter 13 positions away, preserving ASCII case. Digits, punctuation, whitespace, Romanian diacritics, and every other Unicode character remain unchanged. ROT13 is its own inverse and provides no confidentiality, authentication, or meaningful obfuscation against anyone familiar with it.
Runs locally — files stay on your deviceHow do I reverse ROT13?
Apply ROT13 to the output again.
A fixed substitution over 26 ASCII letters
A 13-position rotation divides the Latin alphabet into pairs, making the same operation both encoder and decoder.
How it works
A case-insensitive ASCII-letter regex finds characters, then character codes are rotated within uppercase or lowercase A–Z ranges.
Key concepts
Involution
Applying the operation twice restores the original ASCII letters.
ASCII scope
ă, î, â, ș, and ț are unchanged.
When to use it
- Reproduce a classic puzzle transformation.
- Lightly obscure spoilers where ROT13 is customary.
- Test a reversible substitution example.
When not to use it
- Do not protect passwords or private text.
- Do not expect Romanian or other alphabets to transform.
- Do not call it modern encryption.
Worked examples
Classic
- Input
Hello- Expected output
Uryyb
Case is retained.
Twice
- Input
Uryyb- Expected output
Hello
The same mapping reverses it.
Romanian
- Input
Bună!- Expected output
Ohañ!
ASCII letters rotate; ă and punctuation remain.
Common mistakes
Treating it as encryption
No key or security exists. Correction: Use authenticated encryption.
Expecting all alphabets
Only ASCII Latin letters match. Correction: Choose a defined cipher/alphabet.
Using a separate decoder expectation
Encoder and decoder are identical. Correction: Apply ROT13 again.
Best practices
- Label ROT13 output clearly.
- Use it only for non-sensitive conventions.
- Preserve original Unicode text when round-trip testing.
Related operations and differences
ROT13 Decoder
Choose ROT13 Decoder when you need to decode ROT13 text locally.; use ROT13 Encoder specifically for rot13.
Base64 Encoder
Choose Base64 Encoder when you need to encode text as Base64 in your browser.; use ROT13 Encoder specifically for rot13.
Text to Binary
Choose Text to Binary when you need to encode text as 8-bit binary groups.; use ROT13 Encoder specifically for rot13.
Text to Hex
Choose Text to Hex when you need to encode UTF-8 text as hexadecimal.; use ROT13 Encoder specifically for rot13.
URL Encoder
Choose URL Encoder when you need to encode unsafe characters while preserving URL structure.; use ROT13 Encoder specifically for rot13.
Base64 Decoder
Choose Base64 Decoder when you need to decode Base64 into readable text.; use ROT13 Encoder specifically for rot13.
Limitations and privacy
- ASCII A–Z and a–z only; no key, alphabet option, security, integrity, or locale support.
The entered value is transformed locally in this browser and is not sent to the Toolbox server.
Copying or pasting sensitive output into another service is a separate disclosure decision.
Frequently asked questions
Are digits changed?
No.
Are diacritics changed?
No.
Is case preserved?
Yes.
Is ROT13 secure?
No.