Caesar Cipher

About this calculator

This tool applies the Caesar cipher, one of the oldest known encryption methods (reportedly used by Julius Caesar for military messages), which shifts every letter in the text a fixed number of positions through the alphabet — a shift of 3 turns A into D, B into E, and so on, wrapping back to the start once it passes Z. Entering a negative shift reverses the process, decrypting text that was encrypted with the corresponding positive shift.

It's used today mainly for teaching the basic concepts of cryptography — substitution, key space and how easily a shift cipher can be broken by trying all 25 possible shifts or by frequency analysis — as well as for puzzles, escape rooms, and lightweight obfuscation where real security isn't the goal, since the cipher offers essentially none against a determined attacker.