Caesar Cipher

Shift Latin letters with a configurable Caesar cipher. The conversion runs live in your browser, while all other characters remain unchanged.

Choose a value from 0 to 25.

Letters are converted as you type. Other characters remain unchanged.

What this tool does

A Caesar cipher replaces each Latin letter with a letter at a fixed distance in the alphabet.

ROT13 is a Caesar shift by 13 positions and reverses itself when it is applied a second time.

How to use the tool

  1. Type or paste text into the input field.
  2. Choose the number of positions and the direction of the shift.
  3. Use ROT13 for the fixed 13-position shift, then copy the output when needed.

Useful applications

  • Explore how classic monoalphabetic ciphers work in a lesson or exercise.
  • Read text with a known shift by selecting the same number of positions in the opposite direction.
  • Use ROT13 for simple spoiler notices when confidentiality is not required.

Notes and limitations

  • A Caesar cipher is not secure and must not be used to protect confidential information.
  • Only ASCII letters A to Z and a to z are shifted. Accented letters, numbers, whitespace and punctuation remain unchanged.
  • The conversion runs entirely in the browser, so the entered text is not transmitted to petuja.tools for this feature.

Frequently asked questions

How do I decode text shifted with a Caesar cipher?

Choose the same number of positions that was used to encode the text, but select the opposite direction.

Is ROT13 secure encryption?

No. ROT13 is an easily reversible Caesar shift and is suitable only for simple obfuscation, not for protecting confidential data.

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