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Cipher Encoder / Decoder

Solve a secret message automatically, or encode and decode Caesar, Vigenère, Morse and more.

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Cipher

Don't know the cipher or shift? Tries every one.

Most likely answer

Found using Caesar shift 3. Not right? Check the other guesses below.

All guesses, most English-like first

The solver checks every Caesar shift and Atbash, scoring each result on English letter patterns and common words. Vigenère needs the keyword, so it can't be guessed here.

Classic Ciphers, All in One Tool

Whether you're building a puzzle, running an ARG, teaching the basics of cryptography, or working through a CTF challenge, this tool covers the ciphers that come up most: Caesar (with an adjustable shift and a genuine auto-solve mode), ROT13, Atbash, Vigenère, and Base32 encoding.

How to Use This Tool

  1. 1Choose a cipherCaesar, ROT13, Atbash, Vigenère, or Base32.
  2. 2Enter your text and any needed keyCaesar needs a shift number, Vigenère needs a keyword — ROT13 and Atbash need nothing extra.
  3. 3Switch between encode and decodeFor ciphers where it matters — ROT13 and Atbash are self-reversing, so there's nothing to switch.
  4. 4Try auto-solve on a Caesar cipherDon't know the shift? Paste the ciphertext in decode mode and see every possible shift ranked by how closely it matches real English.

Good to Know

  • The Caesar auto-solve uses a real cryptanalysis technique — chi-squared scoring against standard English letter frequency — not a hardcoded answer key.
  • ROT13 is its own inverse: running it twice returns the original text, which is why there's no separate decode mode for it.
  • Vigenère is significantly harder to crack than Caesar since the shift changes with each letter of the keyword — a good next step once Caesar makes sense.
  • Base32 here is a plain encoding (not encryption) — useful for TOTP secrets and certain URL-safe encodings, included alongside the classic ciphers since it uses the same "text ↔ text" workflow.

Frequently Asked Questions

What's the difference between a cipher and encoding like Base32?

A cipher (Caesar, Vigenère, Atbash) is meant to hide meaning and typically needs a key to reverse. An encoding like Base32 has no secrecy goal at all — it just represents the same data in a different, URL/text-safe character set, and anyone can reverse it without a key.

Are these ciphers actually secure?

No — none of these classic ciphers are secure by modern standards. They're genuinely useful for puzzles, ARGs, teaching cryptography basics, and CTF challenges, but not for protecting anything sensitive.

How does the Caesar auto-solve work?

It tries all 25 possible shifts and scores each result against standard English letter-frequency statistics (a chi-squared style comparison) — the shift producing the most English-like letter distribution is ranked first.

Does the Vigenère key need to be a real word?

No — any sequence of letters works as the key. A real word is just easier to remember and share.