Free Caesar Cipher Tool
Quick Tips
- • This tool runs entirely in your browser - your data stays private.
- • Press Ctrl+V (Cmd+V on Mac) to quickly paste text.
- • Use the Copy button to save your result to clipboard.
- • Bookmark this page for quick access!
Encrypt and decrypt using Caesar cipher with customizable shift value.
Your Recent Tools
Examples
HELLO (shift 3)
KHOOR
KHOOR (shift -3)
HELLO
Attack at dawn
Dwwdfn dw gdzq
The quick brown fox
Wkh txlfn eurzq ira
Why Use This Tool?
What problems does this solve?
Learn classical cryptography, create simple puzzles, or decode messages from escape rooms and games. The Caesar cipher is educational and entertaining, not secure.
Common use cases:
- Learning fundamental cryptography concepts
- Creating puzzles and escape room challenges
- Solving CTF and geocaching ciphers
- Educational demonstrations of substitution ciphers
- Quick message obfuscation (not secure)
Who benefits from this tool?
Students learning cryptography. Puzzle creators and escape room designers. CTF and geocaching enthusiasts. Teachers demonstrating cipher concepts.
Privacy first: All encoding happens locally in your browser. Your text never leaves your device.
Frequently Asked Questions
According to ancient historian Suetonius, Caesar used a shift of 3, replacing A with D, B with E, and so on. This is sometimes called the "original" Caesar cipher.
Only 25 meaningful keys (shifts 1-25). Shift 0 and shift 26 produce the original text. This small keyspace makes brute force trivial.
Try all 25 shifts (brute force) or use frequency analysis. In English, E is most common (~13%), followed by T, A, O, I, N. The most frequent ciphertext letter likely represents E.
To decrypt, use the negative of the encryption shift, or equivalently, 26 minus the shift. Encrypt with +3 means decrypt with -3 (or +23).
Because each letter is substituted with a different letter. The substitution is fixed throughout the message (unlike Vigenère which varies substitution). This uniformity makes it vulnerable to frequency analysis.
No legitimate security use. It appears in puzzles, escape rooms, CTF competitions, and education. Recognizing Caesar-encrypted text is a basic puzzle-solving skill.
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