ROT13 / Caesar Cipher
Apply ROT13 or a custom Caesar cipher shift to text. Great for simple obfuscation and puzzles.
About This Tool
The ROT13 & Caesar Cipher tool encodes and decodes text using classical substitution ciphers. ROT13 shifts each letter by exactly 13 positions in the alphabet. Because the alphabet has 26 letters, applying ROT13 twice returns the original text — it is its own inverse. The Caesar cipher allows any custom shift from 1 to 25.
Only alphabetic characters are shifted; numbers, spaces, and punctuation pass through unchanged. These ciphers provide trivial obfuscation only and must not be used for any security purpose.
How to Use
- Select the cipher: ROT13 (fixed shift of 13) or Caesar (custom shift).
- For Caesar cipher, set the shift value (1–25) using the slider or input.
- Type or paste your text in the input area.
- Click Encode / Decode — for ROT13, encode and decode are the same operation.
- Click Copy to copy the output.
Use Cases
Online communities use ROT13 to hide spoilers in text that readers can choose to decode. Puzzle designers embed ROT13 clues in games, ARGs, and escape rooms. Students in computer science courses learn substitution ciphers as an introduction to cryptography. Developers encode mildly sensitive strings in configuration files to prevent casual reading (not for security).
FAQ
- Is ROT13 secure? — No. ROT13 and Caesar ciphers provide no cryptographic security. They are trivially reversible without a key.
- How do I decode ROT13? — Apply ROT13 again to the encoded text. Encoding and decoding ROT13 are identical operations.
- What shift did Julius Caesar use? — Caesar reportedly used a shift of 3 (A→D). ROT13 uses a shift of 13, which is self-inverse for the 26-letter Latin alphabet.