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Caesar Cipher Online
Encrypt, decrypt, or break a Caesar cipher with Latin, Polish, or custom alphabets.
Runs in your browserProcessed locally. Your input never leaves your device.
Brute force tries every meaningful shift and ignores the selected shift value.
13 produces ROT13. Brute-force mode ignores this value.
Details
About this tool
Encrypts and decrypts text with a Caesar shift, or tries every possible shift when the key is unknown. Choose the 26-letter Latin alphabet, the 32-letter Polish alphabet, or provide your own ordered alphabet. Letter case, spaces, numbers and punctuation are preserved, so the result is ready to copy rather than a cleaned-up approximation.
A Caesar cipher replaces every letter with the letter a fixed number of positions later in the alphabet. With a shift of 3, A becomes D and Z wraps around to C. Decryption moves in the opposite direction. ROT13 is the same idea with a shift of 13 in the Latin alphabet; applying it twice returns the original text.
If the shift is unknown, brute force is the reliable approach because the key space is tiny. A Latin Caesar cipher has only 25 meaningful shifts. The tool displays all of them and uses letter frequencies plus common words to put the most plausible English or Polish result first. Short messages and names can have several believable answers, so the complete list remains visible.
The Polish alphabet is treated as its own 32-letter sequence, including Ą, Ć, Ę, Ł, Ń, Ó, Ś, Ź and Ż. Letters Q, V and X are not part of that sequence and remain unchanged. A custom alphabet lets you reproduce classroom exercises, game puzzles and historical variants without changing the code.
This is an educational cipher, not modern encryption. Anyone can test every shift in milliseconds, so it must never be used for passwords, private messages or confidential files. Everything runs locally in the browser and the text is not uploaded.
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Good to know
Questions people actually ask
- Is the Caesar cipher secure?
- No. A Latin Caesar cipher has only 25 meaningful keys, and this tool can test every one in milliseconds. It is useful for lessons, puzzles and historical examples, but never for passwords, private messages or sensitive data.
- How does brute force break a Caesar cipher?
- It decrypts the message with every possible non-zero shift. For the built-in English and Polish alphabets, the results are ranked with letter frequencies and common words. The complete list stays visible because a short message can have more than one plausible reading.
- What is ROT13?
- ROT13 is a Caesar shift of 13 in the 26-letter Latin alphabet. Thirteen is exactly half the alphabet, so applying ROT13 a second time restores the original text. It is commonly used to hide spoilers and puzzle answers, not to secure information.
- Does the Polish alphabet change the result?
- Yes. Polish has 32 letters, and Ą, Ć, Ę, Ł, Ń, Ó, Ś, Ź and Ż each occupy their own position. Q, V and X are not part of the standard Polish alphabet, so this mode leaves them unchanged.
- Can I use my own alphabet?
- Yes. Enter each letter once in the order used by the puzzle or exercise. The tool validates duplicate positions, preserves case, and lists every possible shift in brute-force mode. Language ranking is unavailable for a custom sequence.
- Is the text sent to a server?
- No. Encryption, decryption and brute force all run in your browser. The message and custom alphabet never leave your device.