How do I decode a Caesar cipher?

Use the opposite shift. If it was encoded with a shift of n, decode with a shift of 26 minus n. ROT13 decodes with ROT13 again.

Is a Caesar cipher secure?

No. With only 25 possible shifts it is trivial to break, so it is best for puzzles, spoilers and learning, not real security.

Is my text uploaded anywhere?

No. Everything runs in your browser, so your text never leaves your device.

Security & Cryptography

Caesar Cipher (ROT13)

Encode or decode text with a Caesar shift cipher, including the popular ROT13.

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Your text

Shift (0-25)

Result appears here...

ROT13 is its own reverse: apply it again to decode. For other shifts, decode with a shift of 26 minus your value.

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Your input, keys and passwords are never uploaded. Want proof? Load this page, then turn off your internet - the tool still works. For an exact check, open your browser's DevTools Network tab and confirm no data is sent when you use it.

About the Caesar Cipher (ROT13)

A Caesar cipher shifts every letter along the alphabet by a fixed amount, wrapping around from Z back to A.

This tool lets you choose any shift from 0 to 25, with quick presets for ROT13 and the classic shift of three used by Julius Caesar.

ROT13 is a special case that is its own reverse, so applying it twice returns the original text, which makes it popular for hiding spoilers and puzzle answers.

Key features

Any shift from 0 to 25
One-click ROT13 and classic shift-of-three
Live encode and decode
Numbers and symbols pass through unchanged

How to use

1Type or paste your text.
2Choose a shift, or click ROT13 or Classic.
3Copy the encoded or decoded result.

Examples

ROT13

Input: Hello

Output: Uryyb

Each letter is shifted 13 places along the alphabet.

Frequently asked questions

How do I decode a Caesar cipher?: Use the opposite shift. If it was encoded with a shift of n, decode with a shift of 26 minus n. ROT13 decodes with ROT13 again.
Is a Caesar cipher secure?: No. With only 25 possible shifts it is trivial to break, so it is best for puzzles, spoilers and learning, not real security.
Is my text uploaded anywhere?: No. Everything runs in your browser, so your text never leaves your device.

Open a related tool to prepare your files or refine the finished result.