The Caesar cipher shifts each letter by a fixed number (the key). Julius Caesar reportedly used shift 3; you can choose any offset for encoding and decoding.
Overview
Encrypt and decrypt Caesar cipher text with a custom shift. Free tool for puzzles and history lessons—copy paste, adjustable key. Free in your browser on Case…
What this page covers
The Caesar cipher shifts each letter by a fixed number (the key). Julius Caesar reportedly used shift 3; you can choose any offset for encoding and decoding.
Quick answer
Encrypt and decrypt Caesar cipher text with a custom shift. Free tool for puzzles and history lessons—copy paste, adjustable key. Free in your browser on Case… Use it in a browser with no account required, then review the output before publishing or shipping.
About Caesar Cipher Tool
The Caesar cipher shifts each letter by a fixed number (the key). Julius Caesar reportedly used shift 3; you can choose any offset for encoding and decoding.
How to Use Caesar Cipher Tool
Enter text and pick a shift value (e.g. 3). Encode for puzzles or decode a clue you received. Share the shift separately so solvers can decrypt.
When to Use Caesar Cipher Tool
Education: Demonstrate frequency analysis on simple ciphers. Games: Layer Caesar under other puzzle steps. History: Connect students to classical cryptography.
Why Use This Caesar Cipher Tool?
Interactive shifts beat paper wheels when testing multiple keys quickly.
Unicode vs HTML formatting
ROT13 is Caesar with shift 13. Vigenère adds multiple keys—Caesar is the simplest alphabet rotation.
Platform compatibility
Classroom history lessons, escape rooms, and beginner cryptography modules. Not for real secrets.
How to use this tool
- Enter text and pick a shift value (e.g. 3).
- Encode for puzzles or decode a clue you received.
- Share the shift separately so solvers can decrypt.
Getting started
The Caesar cipher shifts each letter by a fixed number (the key). Julius Caesar reportedly used shift 3; you can choose any offset for encoding and decoding.
Privacy and local processing
Caesar Cipher runs in your browser on Case Modify. Typical conversions do not upload your pasted text to our servers for processing.
You still share data with your browser vendor and network as with any website; see our privacy policy for analytics and ads. When you work with secrets, credentials, or personal data, review the output locally before you publish or send it.
Details: privacy policy.
Before you publish
Unicode styling, formatted code, and converted units can look correct in the preview but fail in the target app because of font support, line breaks, or platform limits.
Test a short sample in the destination (bio field, IDE, CMS, or spreadsheet) before you paste a long block.
Workflow tips: how Case Modify works, documentation hub.
Limits to keep in mind
Free browser utilities excel at quick edits, classroom exercises, and copy-paste formatting. They are not a replacement for licensed design software, production build pipelines, or compliance review.
When a platform rejects styled Unicode, fall back to plain ASCII from a case converter or remove formatting before you submit final copy.
Frequently asked questions
How do I break a Caesar cipher?
Try all 25 shifts or use frequency analysis—only 26 possibilities for English.
Caesar vs substitution cipher?
Caesar shifts the alphabet uniformly. General substitution maps letters arbitrarily.
Examples
| Before | After | Notes |
|---|---|---|
| HELLO shift 3 | KHOOR | |
| KHOOR shift -3 | HELLO | |
| Shift 13 matches ROT13 |
Related Tools
ROT13 Encoder: Shift the alphabet by 13 to obscure spoilers or puzzles.
Base64 Encode & Decode: Encode strings to Base64 or decode Base64 payloads back to plain text—ideal for JWT segments, API testing, and quick debugging.
Morse Code Translator: Translate letters to Morse and Morse to text.
Naming Conventions Guide: Naming Conventions Guide