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Atbash cipher

Encode and decode text with the Atbash cipher, reversing the alphabet: A becomes Z, B becomes Y, and so on.

Input

Atbash mirrors the alphabet and is self-inverse.

Nothing is uploaded. Everything is computed locally in your browser.
Atbash

The transformed text appears below.

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A 2500-year-old cipher

Atbash originated with Hebrew scribes over two millennia ago, mapping the first letter of the alphabet to the last (aleph to tav, hence At-Bash). Applied to English, A becomes Z and B becomes Y, preserving case and leaving other characters untouched. Like ROT47 it is self-inverse.

Puzzles and learning

Atbash appears in puzzle hunts, escape rooms and beginner cryptography lessons as the simplest substitution cipher. With no key and a fixed mapping, it offers zero security, but it is a charming first step into classical cryptography.

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Atbash Cipher FAQs

How does Atbash work?
Each letter is replaced by its mirror in the alphabet: A becomes Z, B becomes Y, C becomes X, continuing to M becomes N. Case is preserved; digits and punctuation are unchanged.
Is Atbash the same as ROT13?
No. ROT13 shifts by a fixed 13 positions; Atbash mirrors the alphabet. Both are self-inverse monoalphabetic substitutions, but they produce different outputs.
Where was Atbash used historically?
In the Hebrew Bible (Jeremiah), where names like Babylon appear encoded, and by scribes wanting light concealment of text.
Is it secure?
Not at all. Frequency analysis breaks it instantly since each plaintext letter always maps to the same ciphertext letter.
Decode or encode?
The same button does both: applying Atbash twice returns the original text.
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