What is Caesar Cipher Tool?

Caesar Cipher Tool encrypts and decrypts text using the classic letter-shift cipher. Choose any rotation amount from 1 to 25 to encode your message, or use brute-force mode to try all shifts at once for decryption.

The cipher shifts every letter by a chosen amount, wrapping Z back to A. Spaces and punctuation always pass through unchanged, and digits do too unless you turn on Shift Digits to rotate 0–9 as well. Switch on Brute Force and the tool shows all 25 candidate decryptions in a list so you can eyeball the one that reads as English.

How to use

1. Enter the text you want to encrypt or decrypt in the input field.
2. Set the shift amount (1-25) and choose encrypt or decrypt direction.
3. View the result instantly, or use brute-force mode to see all 25 possible shifts.

When to use

• Setting an escape-room or classroom puzzle that students can crack with a notebook.
• Demonstrating substitution ciphers and frequency analysis in a cryptography lesson.
• Quickly obscuring a punchline or spoiler in a forum post — anyone can decode it.

Result

You want to encode the message 'ATTACK AT DAWN' with a shift of 3. The result is 'DWWDFN DW GDZQ'. Share the shift number with the recipient so they can decode it.

FAQ

How secure is a Caesar cipher in practice?

Not at all by modern standards. With only 25 possible shifts, anyone can try them all in seconds — exactly what Brute Force mode does here. Real secrets need AES or a similar modern algorithm; this is for puzzles and teaching.

What does the letter-frequency chart show me?

It compares the letter counts in your cipher text against typical English frequencies (E around 12%, T near 9%). If the cipher's peak sits two slots right of where E should be, the shift was probably 2.

Why are digits and spaces in my message unchanged?

By default they are, because Caesar's cipher is defined only over the alphabet, which keeps word boundaries visible — one reason long messages are easy to break. If you want numbers encoded too, switch on Shift Digits and the tool also rotates 0–9 by the same amount; spaces and punctuation always stay put.

What's the difference between shift 13 and ROT13?

ROT13 is exactly a Caesar cipher with shift 13. Because 13 is half of 26, encrypting twice with shift 13 returns the original text, which is why ROT13 is its own inverse.

Does the tool handle accented letters like é or ñ?

No. Only A–Z and a–z are shifted; accented characters pass through unchanged. If your message needs them, replace them with their unaccented form before encoding to keep the text consistent.

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