Atbash Cipher

Atbash cipher table

Write the alphabet forwards, then backwards underneath. Each letter swaps with the one in the same column.

How the Atbash cipher works

Atbash mirrors the alphabet: the first letter swaps with the last, the second with the second-to-last, and so on. In English, A↔Z, B↔Y, C↔X, all the way to M↔N in the middle. Because the swap goes both ways, running the text through Atbash a second time gives back the original, so the atbash cipher decoder and the encoder are the same tool. Capital letters stay capital; numbers, spaces and punctuation do not change.

There is no key. Anyone who knows the trick can read an Atbash message, which is why it is used today in puzzles, games and geocaching rather than for real secrets.

Where the name comes from

Atbash began with the Hebrew alphabet. Its first letter, aleph (א), swaps with the last, tav (ת); the second, bet (ב), swaps with the second-to-last, shin (ש). Put together, aleph-tav-bet-shin gives "Atbash". The Hebrew Bible uses it: in the Book of Jeremiah, "Sheshach" is generally read as the Atbash form of "Babel".

This Atbash cipher translator also works on Hebrew text. Paste Hebrew letters and they swap the same way; final forms such as ך and ם are treated as their normal letters.

How we tested

"Svool, dliow!" gave "Hello, world!". "Wizard 123 MN" gave "Draziw 123 NM", and "Use result as input" turned it back. The Hebrew ששך gave בבל, the Jeremiah example above, with the final kaf read as kaf. We ran the page in Chromium at desktop width and at 375 px: no sideways scrolling and no console errors. Not tested yet: Safari on iPhone and Firefox.

Questions

How do I decode an Atbash cipher?

Paste the coded text into the box. Atbash is its own reverse, so the result is the decoded message. On paper, swap each letter with the one in the same column of the table: A with Z, B with Y, and so on.

Is Atbash the same as a Caesar cipher?

No. A Caesar cipher moves every letter forward by the same number of places. Atbash reverses the whole alphabet, so the distance between a letter and its partner changes from letter to letter.

Does Atbash have a key?

No. There is only one Atbash alphabet, so there is nothing to keep secret except the method itself.

Why is it called Atbash?

The name is made from the first Hebrew letter pairs it swaps: aleph with tav and bet with shin, read together as A-T-B-SH.