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Atbash cipher

Encode or decode text with the Atbash substitution cipher (A↔Z, B↔Y…). Paste the text or drop the file; nothing leaves the page either way.

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Atbash cipher works straight from this page — free, instant, nothing to install. It covers A↔Z, B↔Y — adjust any of them and the result follows immediately.

How to use it

  1. Open the tool — no signup or install needed.
  2. Enter your input or adjust the available options.
  3. Get your result instantly, then copy or download it.

Frequently asked questions

What does Atbash cipher do?

Encode or decode text with the Atbash substitution cipher (A↔Z, B↔Y…). Paste the text or drop the file; nothing leaves the page either way.

What does it take into account?

It factors in A↔Z, B↔Y. Change any of them and the output follows immediately.

When would I actually use this?

Verifying a download matches its published checksum, comparing two files without reading them, and generating a signature for an API request.

What is the most common mistake?

Hashing a password with a fast algorithm. MD5 and SHA are built to be quick, which is exactly wrong for passwords — those need a deliberately slow function like bcrypt, scrypt or Argon2.

How is Atbash cipher different from Caesar cipher (ROT13)?

They sit next to each other but answer different questions: Caesar cipher (ROT13) is the one to open when you need it to encode or decode text with a Caesar shift cipher — ROT13 by default. Pick whichever matches what you're starting from — both are free.

Is there a tool for the next step?

ROT47 cipher is the closest one after this: Encode or decode text with ROT47, which rotates all printable ASCII characters. Works on a pasted block or on a file you drop in.

Where do the figures come from?

The digests follow their published specifications and are computed by the browser's own crypto implementation where one exists, so a value can be checked against any other conforming tool.

Further reading

All guides →
ComparisonChecksums Are Not Hashes: CRC-32, Adler-32 and What They Are ForA checksum catches accidents. A cryptographic hash resists an attacker. A hash-table hash spreads keys. Three different jobs, three different families — and here is a CRC-32 collision constructed by hand in 0.11 seconds to show exactly why you cannot substitute one for another.ExplainerThe Caesar Cipher Explained: How Shift Ciphers and ROT13 WorkThe Caesar cipher shifts every letter by a fixed amount. Learn how the shift works, why ROT13 is a special case, how to encode and decode by hand, and why the cipher offers no real security today.GuideWhat a Password Manager Cannot MeasureEntropy prices one attack: offline guessing against a stolen hash. Above roughly 90 bits the number stops deciding anything — and the meter on this site under-reported a random 20-character password in 300 draws out of 300.ExplainerPassword Entropy: What a Strength Meter Cannot KnowEntropy measures the process that produced a password, not the characters in it. H = L x log2(R) is only true when every character was chosen at random — which is exactly why a meter scoring a human-invented password on its character classes is measuring the wrong thing.ExplainerWhat Is Inside a JWT — and What It Does Not ProtectA JWT is signed, not encrypted. Anyone holding the token can decode the payload and read every claim in it. Here is a real token, decoded without any key, plus the three attacks the signature is supposed to stop and the one problem it cannot solve.ComparisonMD5, SHA-1, SHA-256: Which Hash, and For WhatMD5 is broken and MD5 is fine, depending on which of three security properties you needed. Here is what collision resistance, second-preimage resistance and preimage resistance actually mean, which algorithm still has which, and why none of them belongs near a password.