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Atbash Cipher

Transform text with the self-inverse Atbash mirror cipher.

How it is calculated

Atbash is a fixed mirror substitution on the 26 letters A to Z: the letter at position n becomes the letter at position 27 − n, so A↔Z, B↔Y, C↔X and so on. The tool goes through your text one character at a time. Uppercase stays uppercase and lowercase stays lowercase. Digits, spaces, punctuation and any non-English letters such as ç, ö or é are copied unchanged. There is no key, and because the mapping is its own reverse, running the output through the tool again gives back the original.

Worked example

Input: Hello, World!. H (8th letter) becomes S (19th), e becomes v, l becomes o, o becomes l. W becomes D, r becomes i, l becomes o, d becomes w. The comma, space and exclamation mark stay. Result: Svool, Dliow!

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Common mistakes

  • Expecting accented or non-Latin letters to change. Only the 26 basic English letters are mirrored, so a word like "çay" keeps its ç.
  • Treating it as real security. With no key, anyone who knows the method reads it instantly.
  • Trying to decrypt by running a different shift. Atbash is decoded by applying Atbash again, not by shifting.
  • Forgetting that case is kept, so a capital at the start of a sentence stays a capital in the output.

About this calculator

This tool applies the Atbash cipher, one of the oldest known substitution ciphers, originally used for the Hebrew alphabet and later adapted to Latin script. It works by mirroring each letter's position in the alphabet: A becomes Z, B becomes Y, C becomes X, and so on, following the rule that a letter at position n maps to position (27 − n).

Because the mapping is symmetric, Atbash is its own inverse — running the cipher twice returns the original text, so the same tool both encodes and decodes. It's taught in cryptography courses as an introduction to substitution ciphers and appears in puzzles, escape rooms, and historical texts (including some Biblical cryptograms), though it offers no real security since there's only one possible key.

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