Caesar Cipher Encoder & Decoder
A Caesar cipher shifts every letter in your message forward or backward by a fix
Updated
A Caesar cipher shifts every letter in your message forward or backward by a fix
How to use Caesar Cipher Encoder & Decoder
- Type or paste your message and choose Encrypt or Decrypt.
- Set the shift amount (0-25) with the box or slider, or click ROT13.
- Read the result and click Copy, or scan the table below to crack an unknown shift.
About Caesar Cipher Encoder & Decoder
A Caesar cipher shifts every letter in your message forward or backward by a fixed number of places in the alphabet. This tool encrypts and decrypts text with any shift from 0 to 25, offers a one-click ROT13 preset, and shows a full brute-force table of all 25 possible decodes so you can crack a message even when the key is unknown. Case is preserved and spaces, digits, and punctuation pass through untouched. Everything runs locally in your browser, so nothing you type is uploaded or stored.
Frequently asked questions
- How do I decrypt a Caesar cipher if I do not know the shift?
- Paste the ciphertext and look at the 'Every possible decode' table at the bottom. It lists all 25 shifts at once; the correct one is the row that reads as normal, readable text.
- What is ROT13 and how is it related?
- ROT13 is just a Caesar cipher with a shift of 13. Because 13 is exactly half of 26, applying it twice returns the original text, so the same operation both encodes and decodes. Click the ROT13 button to set it instantly.
- Does it keep spaces, capital letters, and punctuation?
- Yes. Only the letters A-Z are shifted. Uppercase stays uppercase, lowercase stays lowercase, and any spaces, digits, or punctuation are left exactly as you typed them.
- Is my text private?
- Completely. All encoding and decoding happens locally in your browser with JavaScript. Nothing you type is sent to a server, uploaded, or saved.
- Is a Caesar cipher secure enough to protect real data?
- No. With only 25 possible keys it can be broken in seconds, as this tool's brute-force table shows. Use it for puzzles, education, and games, not for real security.
- Can I encode non-English characters like accented letters or emoji?
- Accented letters, emoji, and other non-A-Z characters pass through unchanged rather than being shifted. The classic Caesar cipher is defined only over the 26-letter Latin alphabet.