Caesar Cipher Decoder & Encoder
beginnerShift each letter by N positions in the alphabet
What is Caesar Cipher?
The Caesar cipher is one of the oldest and simplest encryption techniques, named after Julius Caesar who reportedly used it to communicate with his generals. Each letter in the plaintext is shifted a fixed number of positions down the alphabet. With a shift of 3, A becomes D, B becomes E, and Z becomes C.
How Caesar Cipher Works
To encode a message: take each letter and move it 3 positions forward in the alphabet (or your chosen shift value). To decode: move each letter 3 positions backward. Non-alphabetic characters like spaces and numbers are left unchanged. The key is the shift number, ranging from 1 to 25.
Caesar Cipher in Pop Culture
The Caesar cipher appears in Dan Brown's "The Da Vinci Code," various escape room puzzles, and was used in the TV show "Gravity Falls" (the end credits used Caesar cipher). ROT13, a Caesar cipher with shift 13, was widely used on Usenet forums.
How to Break Caesar Cipher
With only 25 possible shifts, the Caesar cipher is trivially broken by brute force — try all 25 shifts and read the results. Alternatively, frequency analysis works: the most common letter in the ciphertext is almost certainly E (the most frequent English letter), revealing the shift immediately.
Frequently Asked Questions
How do I decode Caesar Cipher?
Enter your ciphertext in the tool above, select "Caesar Cipher" from the dropdown, choose Decode mode, enter the key, and click the button. Results appear instantly.
What is Caesar Cipher used for?
Caesar Cipher was used since ~58 BC for secret communication. While not secure by modern standards, it's widely used in puzzles, escape rooms, and educational contexts.
How secure is Caesar Cipher?
Caesar Cipher is not secure by modern standards — it can be broken quickly with basic cryptanalysis or brute force. Use it for puzzles and learning, not sensitive data.
Who invented Caesar Cipher?
Caesar Cipher was invented by Julius Caesar around ~58 BC.