Atbash Cipher Encoder/Decoder

Type or paste your text to encode or decode using the classic Atbash monoalphabetic substitution cipher. The tool works both ways because Atbash is its own inverse.

1. Input

We support A–Z and a–z. Non-letters (numbers, spaces, punctuation) are kept unchanged.

2. Output

Result:

3. Examples

Plain:

HELLO

Atbash:

SVOOL

Plain:

Atbash

Atbash:

Zgyzhs

How the Atbash cipher works

The Atbash cipher is one of the oldest known substitution ciphers. It simply reverses the alphabet:

Plain: ABCDEFGHIJKLMNOPQRSTUVWXYZ
Cipher: ZYXWVUTSRQPONMLKJIHGFEDCBA

So:

  • A ↔ Z
  • B ↔ Y
  • C ↔ X
  • ...
  • M ↔ N

This mapping is involutive, meaning that applying it twice gets you back the original message. That’s why the same tool can be used for both encoding and decoding.

Is Atbash secure today?

No. Atbash offers zero real cryptographic security by modern standards. Anyone who knows the method or even just suspects a simple substitution can reverse it immediately. Use it for fun, puzzles, ARGs, or educational demonstrations.