Four classic ciphers, encode or decode live as you type. These are puzzle/learning ciphers, not real security — don't use them to protect anything that actually matters.
How it works
Shifts each letter forward through the alphabet by a fixed number of positions (the shift), wrapping from Z back to A — with a shift of 3, A becomes D and Z becomes C. Only letters move; numbers, spaces, and punctuation pass through unchanged. One of the oldest known ciphers, named for Julius Caesar, who reportedly used a shift of 3 for military messages.
A Caesar cipher with the shift permanently fixed at 13 — exactly half of the 26-letter alphabet. That symmetry means encoding and decoding are the identical operation: run it on a message once to scramble it, run it again and you're back to the original. Common online for hiding spoilers or punchlines, never for real secrecy.
Uses a repeating keyword instead of one fixed shift. Each letter of the keyword sets the shift for the matching letter of your message (A=0, B=1 ... Z=25), then the keyword repeats for the rest of the text — so the same letter in your message can encode differently depending on where it falls. Stronger than Caesar since the shift keeps changing, but still breakable with frequency analysis once someone guesses the keyword's length.
Works on raw bytes rather than just letters. Every byte of your message is combined with a byte from the key using bitwise XOR, with the key repeating as needed to cover the whole message. XOR is its own inverse, so the identical operation both encodes and decodes — apply it once with a key to scramble, apply it again with the same key to restore the original exactly. Output is shown as hex since XOR'd bytes usually aren't valid, printable text.
Key
3
Fixed shift of 13 — encoding and decoding are the same operation.