Caesar Cipher and ROT13
Shift letters to encode or decode a Caesar cipher.
Input
This tool runs entirely in your browser. The data you paste or load is never uploaded.
Result
Enter your input, then run the tool.
About this tool
Encodes or decodes text with a Caesar shift of 1 to 25, including ROT13, preserving case, digits and punctuation. A table of every possible shift helps crack a message when the key is unknown.
How to use it
- Paste the text and choose the shift (13 is ROT13).
- Choose encode or decode.
- Read the result, or scan the table of all shifts to find a hidden message.
Frequently asked questions
Is the Caesar cipher secure?
No. There are only 25 possible keys, so anyone can try them all in seconds, as the table shows. Use it for puzzles, not secrets.
Why is ROT13 its own inverse?
The alphabet has 26 letters, so shifting by 13 twice returns to the start. Encoding and decoding are the same operation.
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