BYTETOOLS

Caesar Cipher Encoder & Decoder

Encode and decode text with the classic Caesar shift cipher, choose any shift from 1 to 25, and brute-force all 25 shifts to crack unknown messages.

Result

Khoor, Zruog!

  • Encode and decode with any shift from 1 to 25
  • Live output as you type or drag the slider
  • Brute-force mode listing all 25 possible decodings
  • Preserves case, spaces, numbers and punctuation
  • One-click copy of the result
  • 100% private, in-browser processing

How to use the Caesar Cipher Encoder & Decoder

  1. 1

    Choose Encode or Decode.

  2. 2

    Type or paste your message into the text box.

  3. 3

    Set the shift amount from 1 to 25 with the slider.

  4. 4

    Read the transformed text update instantly below.

  5. 5

    Turn on brute force while decoding to see all 25 shifts at once.

About the Caesar Cipher Encoder & Decoder

The ByteTools Caesar Cipher encodes and decodes text using the oldest known substitution cipher, where every letter is shifted a fixed number of places along the alphabet. Slide the shift from 1 to 25 and watch the ciphertext update live, or switch to decode to recover the original message.

It is perfect for puzzles, escape rooms, classroom cryptography lessons and CTF warm-ups. When you do not know the shift used, the built-in brute-force view lists all 25 possible decodings at once so you can spot the readable line instantly.

Everything runs locally in your browser with JavaScript. No text is uploaded, logged or stored, so you can experiment with secret messages knowing they never leave your device.

Frequently asked questions

What is a Caesar cipher?

A Caesar cipher shifts every letter of a message a fixed number of positions down the alphabet. With a shift of 3, A becomes D and B becomes E. It is named after Julius Caesar, who reportedly used it to protect military messages.

How do I decode a Caesar cipher without the key?

Turn on brute-force mode while decoding. Because there are only 25 possible shifts, the tool shows every decoding at once and you simply pick the line that reads as plain language. This is why the cipher offers almost no real security today.

What is ROT13 in relation to the Caesar cipher?

ROT13 is a Caesar cipher with a fixed shift of 13. Because 13 is exactly half of 26, applying it twice returns the original text, which makes ROT13 its own inverse. Set the shift to 13 here for the same effect.

Does the Caesar cipher change numbers or symbols?

No. This tool only shifts the 26 letters A to Z, keeping their upper or lower case. Digits, spaces, punctuation and other symbols pass through unchanged, so the shape of your message stays recognisable.

Is a Caesar cipher secure?

Not at all by modern standards. With only 25 keys it can be broken by hand in seconds, and letter-frequency analysis defeats it just as easily. Treat it as a fun puzzle or teaching tool, never as real encryption for sensitive data.

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