Atbash Cipher

You ran into a text where A becomes Z and B becomes Y, or you want a simple cipher for a scavenger hunt, a classroom activity or a kids' puzzle. Atbash mirrors the alphabet: every letter swaps with its opposite, and there is no key to agree on or remember. Paste your text in the left box and the output appears instantly, keeping the original upper and lower case.

It is one of the oldest ciphers known, used by Hebrew scribes; the name comes from aleph-tav-beth-shin, pairing the first letter with the last and the second with the second-to-last of the Hebrew alphabet. In the book of Jeremiah, 'Sheshach' is Babel encoded in Atbash. Since mirroring is its own inverse, applying it twice restores the original, so the same box both encodes and decodes.

It works well for puzzles, treasure hunt clues and historical curiosity. Because the mapping is fixed (A always becomes Z), anyone who knows the trick reads everything, so never protect anything real with it. Digits, punctuation and accented letters pass through unchanged; strip accents first if your text has them and you want a clean puzzle. Everything runs in your browser, nothing is sent anywhere.