ROT13 Encoder & Decoder

Apply the ROT13 or ROT47 Caesar cipher to any text. ROT13 is its own inverse — the same operation both encodes and decodes.

ROT13 shifts each letter 13 positions in the alphabet. Non-letter characters are unchanged. Applying it twice restores the original text.

Input ROT13 Output

ROT47 shifts all printable ASCII characters (33–126) by 47 positions, including letters, digits, and symbols. Like ROT13, applying it twice restores the original.

Input ROT47 Output

Shift the alphabet by any number (1–25). ROT13 is shift 13. To decode, enter the same text with the inverse shift (26 − N).

Shift amount (1–25)

Input Ciphertext

Frequently Asked Questions

The English alphabet has 26 letters. ROT13 shifts by exactly half (13), so shifting twice returns to the original position: A (0) + 13 = N (13), and N (13) + 13 = 26 ≡ A (0). This property only holds for shifts equal to exactly half the alphabet size.

No. ROT13 is a trivial substitution cipher with no cryptographic security. It's used for fun, obfuscation of spoilers, and simple text puzzles — not for protecting sensitive data. Use a modern symmetric cipher (AES-GCM) for real encryption.

ROT47 is a variant that also encodes digits and punctuation (all printable ASCII). It's used on forums and in code to obscure strings that include numbers or symbols — like spoilers with dates or technical jargon with brackets.

How It Works

Choose a Cipher

Select ROT13, ROT47, or Custom Caesar Cipher. ROT13 rotates letters; ROT47 also rotates digits and punctuation; Custom lets you pick any shift.

Type or Paste

Enter text in the input area. The cipher is applied live as you type. Non-applicable characters (spaces, punctuation in ROT13) pass through unchanged.

Copy the Output

The ciphertext appears in the output box. To decode ROT13 or ROT47, simply paste the ciphertext back into the input — the same operation reverses it.

Common Use Cases

Spoiler Hiding

Hide movie or game spoilers in forum posts or emails using ROT13. Readers who know the convention can decode it; others see unreadable text.

Puzzle & Game Clues

Encode hints for escape rooms, treasure hunts, or ARGs using ROT13 or a custom shift. Players must know the cipher to decode the clue.

Cryptography Education

Teach the concept of substitution ciphers and why they're not cryptographically secure. ROT13 is the simplest possible example of a shift cipher.

String Obfuscation in Code

Apply ROT47 to obscure API-response strings or config values in source code comments, making them unreadable without being full encryption.

Forum & IRC Tradition

ROT13 has a long history on Usenet and IRC as a convention for voluntary content warnings. Post ROT13-encoded text when the plain version might be unwanted.