ROT13 Encoder / Decoder

Apply the classic ROT13 Caesar cipher to encode or decode text in the browser

Input

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Output

Output will appear here...

What is ROT13 Encoder / Decoder

Last reviewed: April 18, 2026

ROT13 is a letter-rotation cipher where every A–Z and a–z character is shifted by 13 positions, wrapping through the alphabet. Because 26 / 2 = 13, applying ROT13 twice returns the original text.

Although cryptographically trivial, ROT13 is still widely used to hide spoilers in forum posts, obscure puzzle solutions, mask plain-text answers in CTFs, and redact light content in email signatures or code samples.

Why use it

Instantly obfuscate spoilers or answers without needing a key.
Decode ROT13-protected snippets from forums and Reddit threads.
Teach students how substitution ciphers work.
Solve classic CTF and puzzle challenges that rely on ROT13.
Confirm parity tests — two applications should return the original string.

Features

Classic ROT13 letter rotation
Self-inverse — encode and decode with one click
Leaves digits, spaces, and punctuation untouched
All ROT13 work stays on your device
Great for spoiler tags and CTF warm-ups

How to use ROT13 Encoder / Decoder

Paste your text. Drop plain or ROT13-encoded text into the input area.
Click Run. Every letter is shifted by 13 positions, wrapping through A–Z.
Copy the output. Copy the rotated text back into your forum post or puzzle answer.

Example (before/after)

Plain text

Attack at dawn

ROT13 output

Nggnpx ng qnja

Common errors

Expecting numeric rotation

ROT13 only touches letters — digits and symbols stay the same.

Fix: Use ROT47 or a custom cipher if you need to rotate punctuation and numbers as well.

Accented characters not rotated

ROT13 is ASCII-only by definition.

Fix: Strip accents first with the Remove Accents tool or switch to a Unicode-aware cipher.

Expecting stronger security

ROT13 is not encryption — it is obfuscation.

Fix: Use the AES Encrypt / Decrypt tool for confidential text.

FAQ

Is ROT13 secure?

No. It is a trivial substitution cipher intended for light obfuscation, not confidentiality.

Do I need to toggle encode / decode?

No — ROT13 is self-inverse. Applying it twice returns the original text.

Does it change digits?

No. Only A–Z and a–z are rotated; everything else is left untouched.

What about Unicode letters like é or ñ?

They are not in the classic ROT13 alphabet, so they pass through unchanged.

Can I combine ROT13 with Base64?

Yes — many challenges chain ROT13 and Base64. Paste the result into our Base64 tool afterwards.

Is my text sent to a server?

No. All rotation happens inside your browser.

Related tools

ROT13 pairs naturally with other classical ciphers and casing tools. You can also browse the full Encoders & Decoders category for more options.

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