ROT13 Encoder

What this tool does

ROT13 Encoder rotates letters by 13 places in the alphabet, so applying it twice restores the original. It also offers ROT5 for digits, ROT18 for letters and digits together, and ROT47, which rotates all 94 printable ASCII characters.

ROT13 is a simple letter substitution that replaces each letter with the one 13 positions later: A becomes N, B becomes O, and N wraps round to A. Because the English alphabet has 26 letters, rotating by 13 twice brings you back where you started, so the same operation both encodes and decodes. It has been used since the early Usenet days to hide spoilers, puzzle answers and punchlines from casual reading, not to keep secrets.

This tool applies the classic cipher and its common relatives. ROT5 rotates only the digits 0-9 by five, ROT18 combines ROT13 and ROT5, and ROT47 rotates every printable ASCII character from “!” (33) to “~” (126) by 47 places, which also scrambles digits and punctuation. Case is preserved, characters outside the selected range are left untouched, and the result updates as you type, entirely in your browser.

How to use ROT13 Encoder

1. Type or paste text into the Input box, or click Sample to load a spoiler and its encoded punchline.
2. Choose the Cipher: ROT13, ROT5, ROT18 or ROT47.
3. Read the encoded or decoded result in the Output box as you type.
4. Press “Use output as input” to confirm that applying the cipher again restores the original text.
5. Copy, download or share the output.

Tips for better results

• ROT13 leaves digits and punctuation unchanged, so phone numbers and dates stay readable. Use ROT18 or ROT47 to hide them too.
• ROT47 output can contain characters such as backslashes and quotes, so wrap it in a code block when pasting into forums.
• Accented letters such as é are outside A-Z and are not rotated by any variant.
• For other shift values, use the Caesar Cipher tool, of which ROT13 is the special case with a shift of 13.

Common use cases

• Hiding film or book spoilers in a forum post or group chat.
• Concealing quiz answers so readers can try before they look.
• Solving geocaching hints, which are traditionally written in ROT13.
• Teaching the idea of substitution ciphers and why they are weak.

Common mistakes to avoid

• Using ROT13 to protect passwords or personal data. It has no key and is reversed by anyone in seconds.
• Decoding ROT47 text with ROT13, or the reverse; the variants are not interchangeable.
• Expecting ROT13 to work for non-Latin alphabets such as Greek or Cyrillic, which it ignores.