Security & Cryptography
Atbash Cipher
Encode and decode text with the Atbash substitution cipher.
Free foreverRuns in your browserNo sign-up
Result
100% private - runs entirely in your browser.
Your input, keys and passwords are never uploaded. Want proof? Load this page, then turn off your internet - the tool still works. For an exact check, open your browser's DevTools Network tab and confirm no data is sent when you use it.
About the Atbash Cipher
Encode and decode text with the Atbash cipher, which swaps each letter for its mirror in the alphabet (A becomes Z, B becomes Y).
Because the mapping is symmetric, the same operation both encodes and decodes.
Only letters change; numbers, spaces and punctuation stay the same.
Key features
- Symmetric encode and decode
- Keeps numbers, spaces and punctuation
- Preserves upper and lower case
- Copy the result instantly
How to use
- 1Type or paste your text.
- 2Read the transformed result.
- 3Run it again to decode.
Examples
Encode
Input:
HelloOutput:
SvoolEach letter maps to its mirror in the alphabet.
Decode
Input:
SvoolOutput:
HelloThe same operation reverses it.
Frequently asked questions
- Is Atbash secure?
- No. It is one of the oldest and simplest ciphers, meant for puzzles and learning, not real security.
- Why does encoding twice give the original?
- Atbash is symmetric, so applying it a second time reverses the first, returning the original text.
- Is my data uploaded?
- No. Everything runs in your browser.