ROT13 (Rotate by 13) is a simple letter substitution cipher that replaces each letter with the letter 13 positions after it in the alphabet. A becomes N, B becomes O, and so on. Because the English alphabet has 26 letters, applying ROT13 twice returns the original text — making it self-inverse.

Why is ROT13 used on Reddit?

Reddit has historically used ROT13 to hide spoilers in comment sections, particularly in communities discussing books, films, and games. Users encode spoiler text with ROT13 so readers must actively choose to decode it. Old Reddit even had a built-in ROT13 button for this purpose.

Is ROT13 the same as the Caesar cipher?

ROT13 is a special case of the Caesar cipher with a fixed shift of 13. A Caesar cipher can use any shift from 1 to 25, while ROT13 always uses shift 13. The unique property of shift 13 is that it is self-inverse — encoding and decoding use the same operation.

Does ROT13 encrypt numbers and punctuation?

No. ROT13 only rotates letters (A–Z and a–z). Numbers, punctuation, spaces, and other characters pass through unchanged.

Is ROT13 secure for hiding information?

No. ROT13 provides zero cryptographic security — it is trivially reversible by anyone who recognises it. It is intended only for casual obfuscation (like spoiler tags) rather than secure encryption.

Workspace

Input text

Processed locally — no uploads.

ROT13 is self-inverse — encoding and decoding use the same operation. Paste encoded or plain text and it transforms instantly.

ROT13 output

Output appears here as you type…

Letters to Numbers

Trusted Conversion Tools

ROT13 Decoder & Encoder

Our free ROT13 Decoder instantly encodes or decodes any text using the ROT13 cipher — the letter-substitution system used for Reddit spoilers, Usenet posts, and puzzle hints. Since ROT13 is self-inverse, the same operation works for both encoding and decoding. Paste your text and get the result immediately, with a full ROT13 alphabet table for reference.

Who Is It For?

Reddit & Forum Users

Decoding ROT13 spoiler text in Reddit comments, Usenet posts, and forum threads where ROT13 was used before native spoiler tags existed.

Puzzle & Escape Room Enthusiasts

Decoding ROT13-encoded hints, answers, or clues embedded in puzzle games, escape rooms, and alternate reality games.

Developers & Programmers

Quickly verifying ROT13 output from code, decoding obfuscated strings in source files, or testing cipher implementations.

Students & Cryptography Learners

Understanding the simplest self-inverse cipher as a foundation for learning more complex substitution and transposition ciphers.

Writers & Game Designers

Encoding spoilers, hints, and puzzle answers in ROT13 for publication in forums, blog posts, or game documentation.

How It Works

Paste any plain text or ROT13-encoded text into the input box and the transformed version appears instantly in the output panel — no button press needed. ROT13 is self-inverse: it shifts every letter 13 positions along the alphabet, and because the alphabet has 26 letters, applying the shift twice returns to the original. The same operation encodes and decodes. Non-letter characters (numbers, punctuation, spaces) pass through unchanged.

Features

Real-time ROT13 encoding and decoding as you type
Self-inverse — the same tool encodes and decodes
Swap button to move output back to input for chaining
Character, word, and shifted-letter statistics
Expandable full ROT13 alphabet reference table
One-click copy to clipboard
100% browser-based — your text never leaves your device
No sign-up or installation required

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