Free online Caesar Cipher encryption and decryption tool. Shift letters to encrypt or decrypt text with custom shift values and one-click ROT13. Perfect for learning classical cryptography and creating puzzles. Pure frontend, no data upload.
Enter Content:Type or paste the content you want to process.
Configure Options:Adjust settings as needed.
Get Results:Copy the result once done. All processing is local - no data is uploaded.
The Caesar Cipher is one of the oldest encryption techniques, used by Julius Caesar. It works by shifting each letter in the alphabet by a fixed number of positions. For example, with shift 3: A->D, B->E, C->F. Today's ROT13 (shift 13) is a variant of the Caesar Cipher.
The Caesar Cipher is very insecure by modern standards — it only has 25 possible keys (shifts 1-25) and is easily broken by brute force or frequency analysis. However, it remains useful for teaching classical cryptography, puzzles, and simple text obfuscation.
ROT13 is a Caesar variant with shift 13, handling only letters (A-Z, a-z) — encrypt and decrypt are the same operation since 13 is half of 26. ROT5 handles digits (0-9). ROT47 handles all printable ASCII characters (33-126).
The Caesar Cipher is fundamentally based on Latin alphabet shifting. Chinese characters are not affected by the shift operation. If input contains Chinese text, the tool preserves it unchanged and only shifts English letters.
Two methods: 1) Use the same shift value with Decrypt mode selected; 2) Encrypt with shift = 26 - original shift. ROT13 is most convenient — encrypt and decrypt are identical operations.