Atbash cipher — mirror the alphabet, A becomes Z

How to use the Atbash cipher

1. Type or paste your message into Text.
2. The Atbash result appears at once.
3. Copy it. To decode, paste the coded text into the same box; the same swap turns it back.

What it does and when to use it

Atbash is one of the oldest substitution ciphers. It reverses the alphabet, so the first letter becomes the last and so on. Because the rule never changes, it is easy to do on paper and easy to recognise, which is exactly why it is popular in children’s puzzle books, treasure hunts, escape rooms and TV-show riddles.

Use it to set or solve a puzzle, to show how substitution ciphers work, or to hide a spoiler from a casual glance. Do not use it for anything private. Atbash offers no protection at all.

Related tools: the Caesar cipher shifts letters by a fixed amount, ROT18 rotates letters and digits, and the Vigenère cipher adds a keyword, which makes a puzzle harder to solve by eye.

How it works

Number the letters A = 0 to Z = 25. Each letter x becomes 25 − x:

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

Lowercase letters follow the same table and stay lowercase. Because 25 − (25 − x) = x, doing it twice returns the original letter. The tool changes nothing else and runs in your browser.

Worked examples

Hello         →  Svool
Svool         →  Hello
Wizard of Oz  →  Draziw lu La
Room 42, Café →  Illn 42, Xzué

“Hello” and “Svool” show the self-reversing property. “Wizard of Oz” is a well-known curiosity: “Wizard” becomes “Draziw”, which is “Wizard” spelt backwards, because the letter pairs W–D, I–R, Z–A happen to mirror each other. In the last line, the digits, comma and é pass through unchanged.

Limits and tips

• Single letters and short words are easy to guess. “Z” alone almost always means “A” in an Atbash puzzle.
• If your puzzle uses another alphabet, such as Greek or Hebrew, this tool will not change those letters.
• For a cipher that also scrambles digits and symbols, try ROT47.