Atbash Cipher Encoder / Decoder
Atbash is one of the oldest known substitution ciphers — it simply reverses the alphabet so A becomes Z, B becomes Y, and Z becomes A. Type text in either box and the conversion happens instantly. Because Atbash is its own inverse, the same step both encodes and decodes; there is no key to remember.
Type in either box — the other updates automatically. Letters are transformed; digits, spaces, and punctuation pass through unchanged.
How to use the Atbash Cipher Encoder / Decoder
Type or paste into either text box. Whatever you enter on the left is Atbash-transformed into the right box, and editing the right box transforms back into the left — because the cipher is symmetric, both directions are the identical operation. There is no key field and nothing to configure.
Only the 26 letters A–Z are substituted. Each letter is mapped to its mirror position in the alphabet: the 1st letter swaps with the 26th, the 2nd with the 25th, and so on. Case is preserved, so an uppercase A becomes an uppercase Z. Everything else — numbers, spaces, punctuation, emoji, and other scripts — is passed through untouched, which keeps the structure of your text recognizable.
Use the Copy button under either box to grab that side. The whole conversion runs locally in your browser.
What is the Atbash cipher?
Atbash is a monoalphabetic substitution cipher that originated with the Hebrew alphabet — its name comes from the first, last, second, and second-to-last Hebrew letters (aleph–tav–bet–shin). The rule is to reverse the alphabet: the first letter is replaced by the last, the second by the second-to-last, and so on. Applied to the Latin alphabet, A↔Z, B↔Y, C↔X, all the way to M↔N. Because the mapping is a mirror, applying it twice returns the original text, which is why a single operation both encrypts and decrypts.
As a fixed substitution with no key, Atbash offers no real security. There is only one possible mapping, so anyone who recognizes the cipher can reverse it instantly, and even without recognizing it the letter-frequency pattern of the underlying language survives the substitution and gives it away. Its value today is historical and recreational rather than protective — it appears in puzzles, word games, escape rooms, geocaching clues, and as a gentle introduction to how substitution ciphers work.
The cipher is worth knowing precisely because it is so simple. It illustrates the core idea behind all substitution ciphers — replace each symbol according to a fixed table — while being trivial to compute by hand. More elaborate schemes like ROT13, the Caesar shift, and full keyed substitution alphabets are variations on the same theme, trading Atbash's fixed mirror for a shift or a scrambled key. Understanding Atbash makes those easier to grasp.
Common use cases
- Puzzles and games. Solve or create Atbash clues for crosswords, escape rooms, and geocaching caches.
- Learning ciphers. Demonstrate substitution and the idea of a self-inverse cipher with the simplest possible example.
- Quick obfuscation. Lightly scramble a spoiler or answer so it is not readable at a glance.
- CTF warm-ups. Decode classic Atbash strings that show up in beginner capture-the-flag challenges.