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About ROT13, Caesar & Vigenère Cipher Encoder/Decoder
Classic ciphers are the substitution schemes that shaped early cryptography — ROT13, the Caesar shift, the Vigenère keyword cipher, and Atbash. Each one replaces letters according to a simple rule: ROT13 rotates the alphabet by 13, a Caesar cipher shifts by any amount you choose, Vigenère walks through a repeating keyword, and Atbash mirrors A↔Z. They're perfect for puzzles, CTF challenges, escape rooms, classroom demos, and obscuring spoilers.
This free online cipher tool encodes and decodes ROT13, Caesar, Vigenère, and Atbash text instantly, preserving your capitalisation and leaving spaces, digits, and punctuation untouched. Everything runs entirely in your browser — your text is never uploaded to a server.
A clear warning first: these are not encryption in any modern sense. They offer no real security and can be broken by hand or in seconds by a computer. Use them for fun and learning, never to protect anything that actually matters.
Features
- ROT13, Caesar (any shift 1–25), Vigenère (keyword), and Atbash in one tool
- Encrypt and decrypt with a single click; output updates live
- Preserves case and leaves spaces, numbers, and punctuation unchanged
- Fully offline — nothing you type ever leaves your device
How to use
- Type or paste your text into the input pane.
- Pick a cipher — Caesar reveals a shift stepper, Vigenère a keyword field.
- Choose Encrypt or Decrypt to transform the text.
- Copy the result from the output pane, or clear and start again.
Frequently asked questions
Are classic ciphers secure?
No. ROT13, Caesar, Vigenère, and Atbash provide no real security — they are trivial to break by hand or with a computer. They are great for puzzles and learning, but you should never use them to protect passwords, messages, or any sensitive data. For real protection, use modern encryption such as AES.
What is the difference between ROT13 and a Caesar cipher?
ROT13 is simply a Caesar cipher with a fixed shift of 13. Because the alphabet has 26 letters, shifting by 13 twice returns the original text, which makes ROT13 its own inverse — encrypting and decrypting are the same operation. A general Caesar cipher lets you pick any shift from 1 to 25.
How does the Vigenère cipher work?
Vigenère uses a keyword to choose a different Caesar shift for each letter of your message. The keyword repeats across the text, and only letters advance the key — spaces and punctuation are skipped — so the same letter can encrypt differently depending on its position.
Does this tool send my text anywhere?
No. All encoding and decoding happens locally in your browser using plain JavaScript. Your input never leaves your device, so it is safe to use for puzzle solving and experiments without any network connection.
Related tools
Everything runs locally in your browser — your input is never uploaded.