How to use the ROT13 decoder and encoder
- Paste or type your text into Text to rotate. Clear text empties the box.
- Leave Rotation on ROT13, or pick ROT47, ROT5 or ROT18. A short note under the buttons says what the choice rotates.
- Read the Result, which updates as you type. There is no separate decode step: paste scrambled text to read it, or plain text to scramble it.
- Press Copy result. The line under the result counts how many characters were rotated and how many were left alone.
How ROT13 works
ROT13 replaces each letter with the one 13 places later in the alphabet, wrapping from Z back to A, so A and N swap, B and O swap, and so on up to M and Z. The alphabet has 26 letters and 26 is 2 times 13, so applying ROT13 twice gives back the original text. That is why one box both encodes and decodes. It is a Caesar cipher with a shift of 13. Upper and lower case are kept, and digits, punctuation, spaces and accented letters stay as typed.
Usenet users adopted ROT13 in the early 1980s to hide offensive jokes, puzzle answers and spoilers, so a reader had to choose to decode them (ROT13 on Wikipedia). The same page defines the variants offered here. ROT5 rotates the digits 0 to 9 by 5. ROT18 combines ROT13 for letters with ROT5 for digits. ROT47 rotates the 94 printable ASCII characters from ! (33) to ~ (126) by 47, so symbols and digits change as well.
Worked example
The tool opens with Hello World, ROT13 is its own inverse. on ROT13 and shows:
Uryyb Jbeyq, EBG13 vf vgf bja vairefr.
The status line reads "ROT13 rotated 28 letters and left 10 other characters as typed." The 13 in ROT13 does not move because digits are not letters. Switch to ROT18 and it becomes EBG68, since 1 plus 5 is 6 and 3 plus 5 is 8. Paste the ROT13 result back in and the original sentence returns.
Limits and edge cases
ROT13 is not encryption. It has no key, so anyone who recognizes it can reverse it in a second. It is fine for hiding a spoiler from a casual glance and no good for passwords or private data. Only the 26 English letters rotate, so café becomes pnsé with the é untouched, and other alphabets and emoji pass through unchanged. ROT47 hides digits and punctuation but protects nothing either. Need a different shift? Use the Caesar Cipher. To turn text into a different representation rather than scramble it, try the Base64 Decoder and Encoder or the Text Reverser.
Frequently asked questions
How do I decode ROT13?
Paste the scrambled text into the box. ROT13 is its own inverse, so the same step that encodes also decodes, and the readable text appears in the result.
What is the difference between ROT13 and ROT47?
ROT13 only rotates the 26 letters. ROT47 rotates all 94 printable ASCII characters from ! to ~, so digits and punctuation change too.
Is ROT13 secure?
No. It has no key, so anyone who recognizes it can reverse it instantly. It hides spoilers and puzzle answers from a casual glance and nothing more.
Why is it called ROT13?
ROT is short for rotate. Each letter is rotated 13 places around the alphabet, which is exactly half of its 26 letters.
What are ROT5 and ROT18?
ROT5 rotates the digits 0 to 9 by 5 places. ROT18 applies ROT13 to letters and ROT5 to digits in one pass.
Source: Wikipedia, ROT13. The tool runs in your browser and your text is not uploaded.