Caesar Cipher
Encrypt or decrypt text with the Caesar shift, letting you easily read or compose encrypted messages with a simple offset. Runs in your browser, GDPR-compliant.
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How to use this tool (video)
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Caesar Cipher
The Caesar cipher converter encrypts or decrypts text using the Caesar shift. The Caesar cipher is one of the oldest known encryption methods and was already used by Julius Caesar. Each letter is shifted by a fixed number of positions in the alphabet. The converter works locally in your browser.
How it works
In the Caesar cipher, each letter in the alphabet is shifted by a fixed number of positions. The standard shift is 3 but any shift is possible. For example, with a shift of 3, the letter A becomes D, B becomes E, and Z becomes C. The word "Hello" encrypts to "Khoor". Shifting back by 3 returns the original text. For the letter Z with shift 3, you wrap around to C.
What the tool can and cannot do
The converter can encrypt and decrypt text with any shift between 1 and 25. It works only with Latin letters and leaves digits and special characters unchanged. It cannot produce strong encryption like AES or RSA. The Caesar cipher is considered insecure and is not suitable for protecting sensitive data. It is an educational and toy tool.
Why local processing in the browser
All calculations happen locally in your browser. Your text inputs are never sent to a server. There is no upload and no server log files. You need neither an account nor a registration. After the page loads, the converter works offline too. There is no server that could be attacked and nothing is transmitted over the network. You can encrypt and decrypt as often as you like.
Frequently asked questions
How does the Caesar shift work?
Each letter is shifted by a fixed number of positions in the alphabet. With a shift of 3, A becomes D, B becomes E, and Z wraps to C. Shifting back recovers the original text.
Do I need to be online?
No, after the page has loaded, the converter works offline. The required assets are cached.
Are my data uploaded?
No, your text inputs are never sent to a server. Everything is processed locally in your browser.
Is the Caesar cipher secure?
No, the Caesar cipher is considered very insecure and can be broken easily with modern methods.
Can I choose any shift value?
Yes, you can choose any shift from 1 to 25. The standard shift is 3.
Can the converter encrypt numbers?
No, the converter only encrypts Latin letters. Digits and special characters remain unchanged.