Caesar Cipher
Free Caesar cipher encoder. Shift letters by any number (1-25). Classic encryption used by Julius Caesar. Instant results.
About Caesar Cipher
The Caesar cipher is one of the oldest and simplest encryption techniques. Named after Julius Caesar, who used it to protect military communications, it works by shifting each letter in the plaintext by a fixed number of positions down the alphabet. For example, with a shift of 3, A would become D, B would become E, and so on. The alphabet wraps around, so X becomes A, Y becomes B, and Z becomes C.
How It Works
Our Caesar cipher encoder works with a customizable shift: Choose Your Shift — Select any shift value from 1 to 25. A shift of 13 is called ROT13. Enter Your Text — Type or paste the text you want to encrypt. View Results — Each letter shifts forward by the shift amount. Non-alphabetic characters remain unchanged. To decode, simply use the same shift in reverse (26 - shift).
Common Uses
- Learning cryptography basics
- Puzzles and escape rooms
- Historical interest in ancient encryption
- Simple message obfuscation
- Programming exercises
FAQ
How secure is Caesar cipher?
Very insecure by modern standards. There are only 25 possible shifts, so it can be easily broken by trying all possible combinations. Do not use for sensitive data.
What is ROT13?
ROT13 is a Caesar cipher with a fixed shift of 13. It is commonly used to hide spoilers, answers, or offensive content online. Since the alphabet has 26 letters, applying ROT13 twice returns the original text.
How do I decode Caesar cipher?
If you know the shift amount, simply use the reverse shift (26 - shift). If you do not know the shift, you can try all 25 possible shifts to find one that produces readable text.