How to use
01
Type in the text box
Replace the default Hello, Toolora! with your message or ciphertext. The output recomputes on every keystroke, so you never need to press a convert button.
02
Drag the Shift slider
Move it between 0 and 25; the label shows the current value as ROT followed by the number. To reverse a message encrypted with shift k, set the slider to 26 minus k.
03
Copy the output
A copy button appears above the output box whenever there's a result. Grab the rotated text for your puzzle, spoiler post, or classroom handout.
Why Caesar Cipher
- Caesar (rotation) cipher with adjustable shift 0-25.
- ROT13 (shift 13) is its own inverse, apply twice to decrypt.
- Non-letters pass through untouched.
Common questions
How do I decode a Caesar cipher when the shift is unknown?
Brute force it. There are only 25 possible shifts, so drag the slider slowly from 1 to 25 and watch the output; readable words jump out the moment you hit the right value. It usually takes under a minute.
What slider value reverses a Caesar shift of 3?
Set it to 23, because 3 plus 23 wraps the alphabet fully around. Paste khoor, drag to 23, and hello appears. In general, decoding shift k means encoding with shift 26 minus k.
Is ROT13 really its own inverse in this tool?
Yes. Thirteen is exactly half the alphabet, so shifting by 13 twice moves each letter 26 places, right back where it started. Uryyb becomes Hello at slider position 13, and running Hello through gives Uryyb again.
Can I use this shift cipher decoder on numbers and symbols?
Digits and punctuation pass through unchanged; only A to Z and a to z rotate. If a puzzle shifts digits too, handle those separately, since the classical cipher this implements only defined rotation for letters.
Why isn't a Caesar cipher safe for real secrets?
Because 25 keys can be tried by hand in a minute, and letter frequency gives the shift away even faster: whatever symbol appears most often is probably E. Treat it as a puzzle and teaching device, and use modern encryption for anything that actually needs protecting.
Does the caesar cipher solver preserve capitalization?
Yes. Uppercase letters rotate within A to Z and lowercase within a to z, so Hello with shift 1 gives Ifmmp, capital I included. That makes decoded output much easier to read than all-caps results.
What does the ROT label beside the slider mean?
ROT is short for rotate: ROT5 rotates each letter five positions, ROT13 rotates thirteen. The label updates as you drag so you always know which rotation you're applying, and ROT0 leaves text unchanged.