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ToolWrenEncrypt or decrypt text with the classic Caesar shift cipher, using any shift value.
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Caesar Cipher is a free, private online tool that lets you encrypt or decrypt text with a Caesar shift cipher (any shift 0-25). It runs entirely in your browser, so nothing you enter is uploaded to a server.
Privacy: this tool runs entirely in your browser. Your input is never sent to, received by, or stored on any server — there are no uploads and no tracking of what you enter.
One of the oldest ciphers, it shifts each letter a fixed number of places — Julius Caesar reputedly used a shift of 3. ROT13 is a Caesar cipher with shift 13.
Choose encrypt or decrypt, set the shift, and type your text. Non-letters are left unchanged.
It provides no real security — there are only 25 possible shifts — but it's great for puzzles and learning.
The Caesar cipher is one of the oldest and simplest encryption methods, named after Julius Caesar, who reportedly used it for military messages. It is a substitution cipher that shifts every letter a fixed number of places down the alphabet - with a shift of 3, A becomes D, B becomes E, and so on.
Each letter is moved along the alphabet by the shift amount, wrapping around from Z back to A. Decryption simply shifts in the opposite direction. Non-letters - spaces, digits, punctuation - are left unchanged. So 'HELLO' with a shift of 3 becomes 'KHOOR'. There are only 25 useful shifts (a shift of 0 or 26 changes nothing).
With only 25 possible shifts, a Caesar cipher can be broken in seconds by simply trying every shift (a brute-force attack), or by frequency analysis. It provides no genuine protection and must never be used for sensitive data. Its value today is educational and recreational - it is the perfect introduction to how ciphers work.
ROT13 is just a Caesar cipher with a fixed shift of 13. Because 13 is exactly half of 26, applying it twice returns the original text, which makes it conveniently self-reversing. The general Caesar cipher in this tool lets you pick any shift, of which 13 (ROT13) is one popular special case.
Choose encrypt or decrypt, set the shift amount, and type your text - the result updates instantly. Use it for puzzles, escape-room clues, classroom demonstrations of cryptography, or casually obscuring spoilers. Everything runs in your browser.