Encode or decode text using the ROT13 Caesar cipher. ROT13 replaces each letter with the letter 13 positions after it in the alphabet. Encoding and decoding use the same operation.
Type or paste the text you want to encode or decode into the Input box on the left.
Click the Encode button to convert your text, or Decode to reverse the process. Results appear instantly in your browser with no data sent to any server.
Click Copy Result to copy the output to your clipboard. Use Swap to move the output back to the input box for chained encoding operations.
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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 encoding and decoding identical operations.
ROT13 was historically used in online forums and newsgroups to obscure spoilers, punchlines and offensive content so readers had to actively choose to reveal it. It is also used as a simple example of a substitution cipher in programming and cryptography education. ROT13 provides no real security whatsoever.
No. ROT13 is not encryption at all. It is trivially reversible by anyone who knows the method, which is publicly known and documented. Never use ROT13 to protect sensitive information, passwords or private data. It is only appropriate for light-hearted spoiler protection or educational demonstrations.
No. ROT13 only affects letters (A-Z and a-z). Numbers, spaces, punctuation and special characters pass through unchanged. Only the 26 letters of the English alphabet are rotated. This means ROT13 cannot encode numeric data and leaves special characters fully visible.
ROT13 is a specific instance of the Caesar cipher with a shift of exactly 13. A Caesar cipher can use any shift value from 1 to 25. ROT13 is unique because a shift of 13 (half of 26) means encoding and decoding are the same operation. Other Caesar cipher shifts require different operations for encoding and decoding.
ROT47 is an extension of ROT13 that rotates all 94 printable ASCII characters (from ! to ~) by 47 positions. Unlike ROT13 which only affects letters, ROT47 also encodes numbers and punctuation. Like ROT13, ROT47 is its own inverse so applying it twice returns the original text.
Most languages implement ROT13 easily. In Python: import codecs; codecs.encode("hello", "rot_13"). In PHP: str_rot13("hello"). In JavaScript you can use a character code replacement loop. Our online tool handles this instantly without writing any code.
Standard ROT13 only applies to the 26 letters of the English (Latin) alphabet. For other alphabets such as Cyrillic or Greek, ROT13 is not directly applicable because they have different numbers of letters. ROT47 applies to a broader ASCII character set but still does not cover non-ASCII scripts.
