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Caesar / ROT13 / Vigenère / Atbash Cipher

Four classical letter-substitution ciphers in one tool. **Caesar** shifts every letter by a fixed amount (3 for the original 'Caesar's cipher'). **ROT13** is Caesar with shift 13 — its own inverse, used for spoiler tags. **Vigenère** uses a repeating keyword to vary the shift per letter (strong by hand standards, trivial today). **Atbash** mirrors the alphabet (A↔Z, B↔Y…). For Caesar, a brute-force panel shows all 26 possible decryptions at once.

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Output
  
  
 
How to use
 
     
  1. Pick a cipher and (for Caesar/Vigenère) choose encode or decode.
  2. Type or paste the text. For Caesar, drag the shift slider; for Vigenère, type the key.
  3. Output updates live. The brute-force panel below tries all 26 Caesar shifts when you're trying to crack a message.
    4.  
 
  
 
Frequently asked questions
 
 
 
Are these secure?
 
No — they're educational and used in puzzles. Even Vigenère falls to frequency analysis once the key length is known. Use AES or modern ciphers for real security.
 
 
Why is ROT13 used at all?
 
Spoiler tags, joke punchlines, mild obfuscation. Because it's its own inverse, the same tool encodes and decodes.
 
 
What characters get shifted?
 
Only A-Z and a-z. Numbers, spaces, punctuation, and non-Latin scripts pass through untouched.
 
 
How is the brute-force panel useful?
 
When you know a message is Caesar-shifted but don't know the shift — scroll through all 26 outputs and pick the one that reads as plain text.
 
 
 
    
 
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