--- title: Atbash Cipher: Free Online Tool | Relic description: Free Atbash cipher encoder and decoder. Flip the alphabet so A becomes Z and B becomes Y. Atbash undoes itself, so one box does both. Runs entirely in your browser. canonical: https://relic.space/tools/atbash-cipher source: https://relic.space/llms.txt --- # Atbash Cipher Encoder and Decoder Flip the alphabet so A becomes Z, B becomes Y, and so on. Atbash undoes itself, so the same box encodes and decodes. Runs entirely in your browser. Nothing you type is uploaded. Your text Atbash result Result appears here… The whole key | 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 | | - | - | - | - | - | - | - | - | - | - | - | - | - | - | - | - | - | - | - | - | - | - | - | - | - | - | | 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 | ## How the Atbash cipher works Atbash writes the alphabet backwards and swaps each letter for the one in the same spot. A becomes Z, B becomes Y, C becomes X, and M and N trade places in the middle. There is no key and nothing to set. Because every pair just swaps, running Atbash a second time puts every letter back. So one box does both jobs: paste plain text to encode it, or paste Atbash to decode it. Only A to Z change, and capitals stay capitals. Numbers, spaces, punctuation and accented letters come through as they are. It all runs in your browser. ## A worked example Take HELLO WORLD. H is the 8th letter, so it swaps with the 8th letter from the end, S. E swaps with V, L with O, O with L, W with D, R with I, and D with W. That gives SVOOL DLIOW. Put SVOOL DLIOW back in and you get HELLO WORLD. Some words land on other real words: WIZARD comes out as DRAZIW, which is WIZARD backwards. That only happens because W and D, I and R, Z and A are all mirror pairs. ## Where the name comes from Atbash started with the Hebrew alphabet. The name is built from the letters it swaps: alef (the first letter) with tav (the last), then bet (the second) with shin (the second to last). A-t-b-sh. The [Faculty of Theology and Religion at Oxford](https://www.theology.ox.ac.uk/article/crack-the-code)points to two places it shows up in the Book of Jeremiah. In Jeremiah 25:26, “Sheshach” is Atbash for Babel, meaning Babylon. In Jeremiah 51:1, “Leb-qamai” decodes to Kasdim, the Chaldeans. ## Is Atbash secure? No. With no key, anyone who knows the trick can read it, and anyone who doesn’t can guess it from a short sample. Use it for puzzles, games and notes to a kid who likes codes. If you want a cipher you can change, try the [Caesar cipher](https://relic.space/tools/caesar-cipher) (pick any shift) or the [Vigenère cipher](https://relic.space/tools/vigenere-cipher) (pick a keyword). For anything private, use [Encrypt Text](https://relic.space/tools/encrypt-text). The [types of ciphers](https://relic.space/blog/types-of-ciphers) guide explains how they all fit together. ## Frequently asked questions How do I decode Atbash?+ Paste the Atbash text into the box and read the result. Atbash swaps each letter with its mirror (A and Z, B and Y), so doing it twice puts the text back. Encoding and decoding are the same step. Does Atbash need a key?+ No. There is only one Atbash alphabet, so there is nothing to choose or share. That is also why it gives no real secrecy. Is Atbash the same as ROT13?+ No. Both undo themselves, but ROT13 moves every letter 13 places forward, while Atbash flips the alphabet end to end. HELLO is URYYB in ROT13 and SVOOL in Atbash. Where does Atbash come from?+ It began as a Hebrew cipher. Its name comes from the first letter alef swapping with the last letter tav, and the second letter bet with the second to last, shin. Oxford's Faculty of Theology and Religion notes examples in the Book of Jeremiah, where Sheshach stands for Babel. You just copied that. 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