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ROT13 Encoder & Decoder

Encode and decode text with ROT13, ROT5, ROT18, ROT47, and custom shift ciphers.

Updated

What is the ROT13 Encoder & Decoder?

ROT13 is a classic text obfuscation cipher that shifts each letter 13 positions forward in the alphabet. Originally popularized on Usenet forums, it became the go‑to method for hiding spoilers, offensive jokes, and puzzle solutions — because applying the same shift twice returns you to the original text.

Our ROT13 Encoder & Decoder brings that same simplicity to the modern web, then supercharges it with:

  • Multiple ROT variants — ROT5 for digits, ROT18 for letters+digits, and ROT47 for full printable ASCII.
  • Custom shift — any Caesar cipher offset between 1 and 25.
  • Live character statistics — see letter, digit, and total counts for both input and output.
  • One‑click Swap — instantly feed the output back as input for quick double‑encoding or decoding.
  • Copy to clipboard on every text block.

Whether you’re testing an encoding library, posting an April Fools’ message, or just exploring historic ciphers, this tool gives you everything in one place — no sign‑up, and no data ever leaves your browser.

How it works

All ROT ciphers are Caesar ciphers — they replace each character with another a fixed distance away in a character set.

ROT13 (Letters)

Only A–Z and a–z are affected. Each letter moves 13 places:

  • A → N, B → O, …, M → Z
  • N → A, …, Z → M
  • Same rule for lowercase.

Because the Latin alphabet has 26 letters, shifting by 13 is its own inverse: ROT13(ROT13(text)) == text.

Example:
Hello → Uryyb
Uryyb → Hello

ROT5 (Digits)

Acts on 0–9, shifting by 5. Wrap‑around: 9 → 4, 4 → 9, etc.

Example:
123 → 678
789 → 234

ROT18 (Letters + Digits)

Combines ROT13 for letters and ROT5 for digits in one pass. Useful for alphanumeric strings.

Example:
Pass123 → Cnff678

ROT47 (Printable ASCII)

Shifts every printable ASCII character (codes 33–126) by 47 positions. This includes letters, digits, punctuation, and symbols. Like ROT13, it is self‑inverse because the printable set has 94 characters, and 47 is exactly half.

Example:
Hello! → w6==@C
w6==@C → Hello!

Custom Shift

A pure Caesar cipher on letters (A–Z, a–z) with any shift from 1 to 25. Digits and other characters remain unchanged. Shift 13 is equivalent to ROT13.

Example (shift 5):
abc → fgh

Examples

Basic ROT13 Encoding

Convert a simple message using the classic ROT13 shift.

Hello, World!
Uryyb, Jbeyq!

ROT47 Obfuscation

Encode an email address with ROT47, which covers all printable ASCII.

user@example.com
FD6Co6I2>A=]4@>

Custom Shift (ROT5)

Apply a Caesar shift of 5 to a philosophical quote.

Cogito ergo sum
Htlnyt jwlt xzr

Frequently asked questions

What is ROT13 used for?

ROT13 is primarily used to obscure text — not encrypt it. Historically it hid spoilers, punchlines, and sensitive words on forums and newsgroups. Today it’s handy for puzzles, lightweight obfuscation, and educational demonstrations of substitution ciphers.

Is ROT13 encryption secure?

No. ROT13 is not encryption — it’s obfuscation. There is no key, and the algorithm is publicly known. Anyone can reverse it instantly by applying the same shift again. For real security use modern encryption like AES.

Can this tool decode ROT13?

Yes. Because ROT13 is its own inverse, encoding and decoding are the same operation. Simply paste the encoded text into the input field and the output shows the decoded version. The Swap button makes this even faster.

What’s the difference between ROT13, ROT5, ROT18, and ROT47?

  • ROT13 shifts letters by 13 places.
  • ROT5 shifts digits by 5 places.
  • ROT18 applies ROT13 to letters and ROT5 to digits simultaneously.
  • ROT47 shifts all printable ASCII characters (letters, digits, symbols) by 47 places. Each variant operates on a different character set — choose the one that fits your data.

How do I use a custom shift?

Select “Custom Shift…” from the mode dropdown. A Shift box appears where you can enter any number from 1 to 25. The tool then performs a standard Caesar cipher with that offset, affecting only letters.

Why does the output length stay the same?

ROT ciphers are monoalphabetic substitutions — every character is replaced by exactly one other character. No characters are added or removed, so the output length is always identical to the input length.

Does this tool store my text anywhere?

No. All processing happens entirely in your browser using JavaScript. No text is sent over the network or saved to any server, so your data remains private.

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