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Caesar Cipher

Encode and decode Caesar cipher text with any shift, then brute force all 25 keys to crack it.

Direction

Everything runs in your browser. Nothing is uploaded.

Each letter moves 3 places along the alphabet.

Brute force all 25 shifts

Your text decoded with each key from 1 to 25. Scan for the row that reads as plain language, then click it to apply that shift.

How to decode a Caesar cipher online

  1. Paste your text

    Type or paste the message you want to encode or reveal into the text box.

  2. Set the shift

    Drag the shift slider to the key you want, or tap a preset like the classic 3 or ROT13.

  3. Read or crack the result

    Copy the shifted output, or scan the brute force panel that decodes your text with all 25 keys and click the line that reads as plain text.

Why use this tool

Encode and decode

Shift text one way to scramble a message and the other way to reveal it, switching direction with a single click.

Brute force all 25 shifts

See your text decoded with every possible key at once, so you can spot readable plaintext even when you do not know the shift, then click a row to apply it.

Case and punctuation preserved

Letters keep their upper or lower case while spaces, digits, and punctuation pass straight through untouched.

Any shift, including ROT13

Choose any shift from 0 to 25 with a slider, plus one-tap presets for the classic shift of 3 and self-reversing ROT13.

Runs entirely in your browser

Everything happens on your device with no upload, no account, and no usage limit.

About this tool

The Caesar cipher is one of the oldest and simplest ways to hide a message: each letter is shifted a fixed number of places down the alphabet, so with a shift of three an A becomes D and a Z wraps around to C. It is named after Julius Caesar, who is said to have used it for private correspondence. This tool encodes and decodes Caesar cipher text as you type, keeping upper and lower case intact and passing spaces, digits, and punctuation through unchanged.

Because there are only 25 possible shifts, a Caesar cipher is trivial to break by trying them all. The brute force panel does exactly that, listing your text decoded with every key from 1 to 25 at once so you can scan for the line that reads as plain English, then click it to apply that shift. ROT13, a shift of 13 that is its own inverse, is a common special case you can pick with one tap.

Reach for this when you are solving a puzzle, a geocaching clue, or a capture-the-flag challenge, or when you just want to see how classical ciphers work. For other ways to transform text, try the Morse code translator or the Base64 encoder. The Caesar cipher offers no real security, so never use it to protect anything sensitive.

Frequently asked questions

How does a Caesar cipher work?
Every letter is replaced by the letter a fixed number of positions further along the alphabet. With a shift of 3, A becomes D, B becomes E, and the far end wraps around so X, Y, and Z become A, B, and C. Decoding just shifts each letter back by the same amount.
How do I crack a Caesar cipher without the key?
Paste the coded message and look at the brute force panel below the result. It shows your text decoded with all 25 possible keys at once, so you can scan the list for the one line that reads as plain language and click it to apply that shift.
Does it keep capital letters and punctuation?
Yes. Uppercase letters stay uppercase and lowercase stay lowercase, and everything that is not a letter, including spaces, numbers, and punctuation, passes through exactly as you typed it.
What is ROT13?
ROT13 is a Caesar cipher with a shift of 13. Because 13 is exactly half of the 26-letter alphabet, applying it twice returns the original text, so the same operation both encodes and decodes. Pick the ROT13 preset to use it.
Is my text uploaded anywhere?
No. Everything runs in your browser; nothing is sent to a server, stored, or logged.
Is the Caesar cipher secure?
No. With only 25 possible keys it can be broken in seconds, which is why this tool can brute force it for you. Treat it as a puzzle or a learning tool, never as a way to protect real secrets.

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