What is the Atbash cipher?
Atbash is a substitution cipher that simply reverses the alphabet: the first letter swaps with the last, the second with the second-to-last, and so on. In English, A becomes Z, B becomes Y and M becomes N. The name comes from the Hebrew alphabet, where it was first used: aleph swaps with tav and bet with shin, giving "A-T-B-Sh". Examples of it appear in the Hebrew Bible, in the Book of Jeremiah.
How to use the translator
- Type or paste your text. The Atbash version appears immediately.
- To decode a message, paste it in the same box. Atbash is its own reverse, so encoding and decoding are the same step.
- Use the table below the tool to encode by hand or check individual letters.
How it works
If letters are numbered A = 0 to Z = 25, each letter's position is replaced by 25 minus that position:
C = 25 − P
For example, "W" is position 22, and 25 − 22 = 3, which is "D". Applying the formula twice returns the original letter, which is why the same tool both encrypts and decrypts. Case is preserved, and numbers, spaces and punctuation are not changed.
Example
The word "HELLO" becomes "SVOOL", and "SVOOL" becomes "HELLO" again. The phrase "Wisdom" becomes "Drhwln".
Security and uses today
Atbash has no key, so once someone knows the method, every message can be read instantly. It offers no real security. Today it is used in puzzles, escape rooms, treasure hunts, geocaching and classroom lessons about the history of codes. It is also a good way to show students how a substitution cipher works before moving on to the Caesar and Vigenère ciphers.
Frequently asked questions
Is Atbash a type of Caesar cipher?
No. A Caesar cipher shifts the alphabet; Atbash mirrors it. Both are monoalphabetic substitution ciphers.
Which letters stay the same?
None. In a 26-letter alphabet, every letter changes; the middle pair M and N swap with each other.
Can I use it with numbers?
Classic Atbash only covers letters, so digits are left as they are.