Text Tools
ROT13 Cipher
Encode or decode text with ROT13, the classic letter-shift cipher used to hide spoilers and puzzle answers.
About the ROT13 Cipher
This tool encodes and decodes ROT13, the classic letter-shift cipher used to hide spoilers and puzzle answers, plus ROT18, ROT47 and a Caesar cipher with any shift. The result updates as you type, and a letter wheel shows exactly how each letter is swapped.
What you can do with the ROT13 Cipher
- Four ciphers: ROT13, ROT18, ROT47 and a Caesar shift of any size.
- Live result: Updates as you type, and decoding is the same step.
- Letter wheel: Shows exactly which letter becomes which.
- Spoiler-friendly: Hide puzzle answers and spoilers in plain sight.
Where ROT13 came from
ROT13 became popular on Usenet discussion groups in the early 1980s as a way to hide spoilers, puzzle answers and punchlines, so readers had to choose to decode them. It's a special case of the Caesar cipher, which Julius Caesar is said to have used with a shift of three, try it with the Caesar option.
What each mode changes
ROT13 and the Caesar shift change only the letters A–Z. ROT18 also turns digits 0–4 into 5–9 and back. ROT47 shifts every visible character from ! to ~, including punctuation. Spaces and emoji are always left alone.
It is not encryption
Anyone can reverse these ciphers instantly, so they provide no security. Use them to hide spoilers from casual glances or for puzzles, never to protect real secrets.
Related tools
Frequently Asked Questions
How do I decode ROT13?
Paste the encoded text, ROT13 is its own reverse, so the result is the original. Or tap "Use result as input".
How do I decode a Caesar cipher?
Choose Caesar shift, set the same shift that was used, and pick Decode. If you don't know the shift, try values until the text makes sense.
Is ROT13 safe for passwords?
No. It's trivial to reverse and offers no protection.
Why does ROT13 encode and decode with the same step?
The English alphabet has 26 letters, and ROT13 shifts each one by 13, exactly half. Shifting twice moves a letter 26 places, back to where it started. ROT18 and ROT47 have the same property.
Does ROT13 change numbers and punctuation?
No. ROT13 only shifts English letters A to Z, so digits, spaces and punctuation stay the same. Choose ROT18 to rotate digits by 5 too, or ROT47 to rotate letters, digits and most symbols.
What is ROT47?
ROT47 shifts every visible ASCII character from ! to ~, a set of 94 characters, by 47 places. Letters, digits and symbols like @ and # all change, while spaces stay put. Like ROT13, running it again decodes it.
How do I crack a Caesar cipher if I do not know the shift?
Choose Caesar shift and Decode, paste the message, then move the slider from 1 to 25 until the result reads as normal words. With only 25 possible shifts, this takes under a minute.
Is a Caesar shift of 13 the same as ROT13?
Yes. A Caesar cipher with a shift of 13 gives exactly the same result as ROT13, and encoding and decoding become the same step. Julius Caesar is said to have used a shift of 3.
Are capital letters kept?
Yes. Uppercase letters stay uppercase and lowercase stay lowercase after the shift, so "Hello" becomes "Uryyb" in ROT13. Line breaks and spacing are also kept, so paragraphs keep their layout.
How do I read the letter wheel?
Each box shows a plain letter on top and the letter it becomes underneath for the current setting. In ROT13, A becomes N. In Caesar mode the wheel follows the slider and the Encode or Decode choice.
Does it work for Hindi or other non-English text?
Only the English letters A to Z are shifted. Hindi, Tamil, accented letters and emoji are left as they are, so a mixed message is only partly hidden. ROT47 also covers digits and symbols but not other scripts.
Related tools
- Word & Character Counter, Count words, characters (with and without spaces), sentences and paragraphs, plus reading and speaking time, live as you type.
- Palindrome Checker, Check whether a word, phrase or number reads the same forwards and backwards, ignoring spaces, punctuation and capitals.
- Find & Replace, Find every occurrence of a word or phrase and replace it, with match-case and whole-word options and a count of replacements.
- Lorem Ipsum Generator, Generate Lorem Ipsum as paragraphs, sentences, words or list items, in short, medium or long lengths, as plain text or HTML.
- Text Diff Checker, Compare two versions of a text line by line or word by word, see what was added or removed, and how similar they are.
- JSON Formatter & Validator, Format, validate and minify JSON, spot syntax errors and turn messy JSON into readable, indented text or a compact single line.
Quick Work Studio