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Atbash Cipher: Mirror Alphabet Encoder and Decoder

This free Atbash cipher tool swaps each letter with the one at the opposite end of the alphabet, so A becomes Z and B becomes Y. Because the swap is symmetrical, the same step encodes and decodes.

By Debmedia Technologies LLP · Kolkata, India · Updated

What Is It and When Do You Need It?

Atbash is a mirror cipher. The name comes from the Hebrew letters aleph, taw, beth and shin, the first and last letters and the second and second-last. It is found in old texts and in modern puzzles.

Paste text and the tool flips it. Paste the result again to get the original back.

How to Use This Tool

  1. Type or paste your text.
  2. Press Run.
  3. Copy the result.
  4. Run it again on the result to check you get the original.

How the Calculation Works

Each letter at position p (0 for A, 25 for Z) is replaced by the letter at position 25 − p. So A is Z, B is Y, and M is N. Case is kept and other characters are not changed.

Worked Example

HELLO becomes SVOOL. Attack at dawn becomes Zggzxp zg wzdm.

Common Uses

  • Puzzles and games.
  • Teaching substitution ciphers.
  • Quick message hiding for fun.
  • Studying historical ciphers.

Tips and Common Mistakes

  • There is no key, so it is not secure.
  • Combine with the Caesar cipher for harder puzzles.
  • Only letters A to Z are changed.

Next, you may need the Caesar cipher, A1Z26 cipher, affine cipher, Vigenère cipher.

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Frequently Asked Questions

A simple substitution cipher from Hebrew scribes in which the first letter of the alphabet is swapped with the last, the second with the second last, and so on.
No. Applying Atbash twice returns the original, so one step does both.
Yes. Digits, spaces and punctuation are left unchanged.
No. It has no key, so anyone who knows the method can read the message.

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