ROT13 / Caesar Cipher
Encode and decode text using ROT13 and Caesar cipher substitution.
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.
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).
- Type or paste your text in the input area.
- Click Copy to copy the encoded output.
Use Cases
Online communities use ROT13 to hide spoilers in text. Puzzle designers embed ROT13 clues in games and escape rooms. CS students learn substitution ciphers as an intro to cryptography. Developers use it for mild obfuscation in config files.
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.