Atbash Cipher Encoder and Decoder
Encode and decode text with the Atbash cipher, where A becomes Z, B becomes Y and so on. No key needed, the same step does both. Free, runs in your browser.
How it works
The Atbash cipher replaces every letter with its mirror image in the alphabet: the first letter with the last, the second with the second to last, and so on. A becomes Z, B becomes Y, C becomes X, and M and N swap with each other. Numbering the letters A = 0 … Z = 25, a letter at position i becomes the letter at position 25 − i. There is no key, so the cipher has one fixed alphabet. Applying it twice gives back the original text, which means the same step both encodes and decodes: paste plain text to encode it, or paste Atbash text to decode it. Only the letters A to Z are changed and their upper or lower case is kept. Digits, spaces, punctuation, letters of other alphabets and emoji stay as they are. The name comes from the Hebrew alphabet, where the first letter aleph is paired with the last letter tav, and the second letter beth with shin: A-T-B-Sh.
Example: HELLO becomes SVOOL, and SVOOL becomes HELLO again. Hello, World! becomes Svool, Dliow!
Frequently asked questions
How does the Atbash cipher work?
Each letter is replaced by the letter in the same place counted from the other end of the alphabet. A and Z swap, B and Y swap, and so on up to M and N.
How do I decode Atbash?
Paste the Atbash text into the box. The cipher reverses itself, so decoding is the same step as encoding and the original message appears right away.
Does the Atbash cipher need a key?
No. The substitution is fixed, so anyone who knows the cipher can read the message. That is why it is used for puzzles and learning rather than for secrets.
What is the Atbash alphabet?
Plain: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z. Atbash: Z Y X W V U T S R Q P O N M L K J I H G F E D C B A.
What happens to numbers, spaces and punctuation?
They are copied unchanged. Only the letters A to Z are mirrored. Letters with accents, such as é or ł, are left as they are.
How is Atbash different from the Caesar cipher?
The Caesar cipher moves every letter forward by the same number of places and needs that number as its key. Atbash reverses the alphabet and has no key, so it is not a Caesar shift: the order of the letters is flipped, not moved.
Is the Atbash cipher secure?
No. It has a single fixed mapping and can be solved at a glance, so do not use it for real secrets.
Is my text sent to a server?
The conversion runs in your browser and your text is not sent anywhere.
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A classical cipher for puzzles and learning. It does not protect real secrets.