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Playfair Cipher: How to Encode & Decode It
Playfair cipher explained: how to build the 5x5 key square, the row/column/rectangle encoding rules, and a full worked example by hand.
Caesar cipher
Encode or decode text with a classic shift cipher. Free, private — nothing leaves your device.
0 characters
Ciphertext0 characters
Your Caesar-shifted text will appear here.Everything you need to shift a message
Live encode and decode
The result updates instantly as you type — no button to click.
Any shift, 1 through 25
Drag the slider to any shift amount, not just the classic shift-3.
One-click swap
Swap the output back into the input and flip the mode to check your work.
100% private
Runs entirely in your browser. Nothing you type is uploaded or stored.
Encode or decode in three steps
- 1
Type or paste your text
Enter the plain text you want to encode, or the ciphertext you want to decode.
- 2
Pick a shift and a mode
Choose how many letters to shift (1-25) and whether you're encoding or decoding.
- 3
Copy the result
The shifted text updates live as you type — copy it or download it as a .txt file.
Built for learning, puzzles, and quick checks
A Caesar cipher is one of the oldest and simplest substitution ciphers — useful for teaching, puzzles, and historical curiosity, not for real security.
Learning cryptography basics
See substitution ciphers work in real time — a common first topic in intro crypto and CS courses.
Puzzles and escape rooms
Caesar ciphers are a staple of puzzle hunts and escape-room clues — decode one in seconds.
Checking a homework answer
Verify a hand-worked shift cipher answer instantly instead of re-counting the alphabet.
Historical curiosity
Try the exact technique attributed to Julius Caesar for secret military correspondence.
Frequently asked questions
What is a Caesar cipher?
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A Caesar cipher shifts every letter in a message forward through the alphabet by a fixed number of positions. Shift 3 turns A into D, B into E, and so on — named for Julius Caesar, who reportedly used it for military messages.
How do I decode a Caesar cipher if I don't know the shift?
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Try each shift from 1 to 25 — there are only 25 possible shifts, so it's fast to check by eye, or look for a shift that produces readable English words. This tool doesn't auto-detect the shift; move the slider until the output makes sense.
Does this tool handle spaces and punctuation?
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Yes — only letters A-Z and a-z are shifted. Numbers, spaces, and punctuation pass through unchanged, and letter case is preserved.
Is a Caesar cipher secure?
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No — it's a classical, educational cipher with only 25 possible shifts, so it can be broken instantly by brute force or letter-frequency analysis. Don't use it to protect anything sensitive.
Is my text uploaded anywhere?
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No. Everything runs in your browser — nothing you type is sent to a server.
What's the difference between a Caesar cipher and ROT13?
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ROT13 is a Caesar cipher with the shift fixed at 13. Because 13 is half of 26, applying ROT13 twice returns the original text — a property most other shifts don't share.
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Try the Caesar cipher now
Free, no account needed.