Caesar Cipher Shifter

Explore the classic Caesar cipher with our smart Caesar cipher shifter — a powerful encoder and decoder in one simple tool. Originally used by Julius Caesar to protect military messages, this shift cipher works by shifting each letter of the alphabet by a fixed number of positions. Our Caesar cipher encoder transforms plain text into secret messages instantly, while the decoder helps you translate Caesar cipher texts back into readable form.

In the article below, you'll not only learn how to use this Caesar cipher solver but also discover the fascinating history behind this ancient technique. We'll explore topics such as:

• What is the Caesar cipher?
• How does the Caesar cipher work?
• How to encrypt and decrypt using the Caesar cipher?
• How to translate Caesar cipher text?

Are you curious about the cipher's inner workings? Uncover more secrets behind this timeless encryption method in our topic-specific guides "How to break a Caesar cipher?" and "What is a shift cipher?"

The Caesar cipher is one of the oldest and simplest encryption methods known to humankind. Named after Julius Caesar, this classic shift cipher was reportedly used by the Roman general and ruler to protect sensitive military communications over 2,000 years ago. According to ancient historians, when Caesar had something secret to say, he would scramble the letters in his messages by simply shifting each letter three steps forward in the alphabet. In his system, A became D, B became E, and so on. Learn more about its origins and the historical context in our dedicated article "Who created the Caesar cipher​?"

Despite its simplicity, the Caesar cipher remained in use for centuries, laying the groundwork for modern cryptography. Today, it remains a classic tool for exploring how encryption works: practical, lightweight, and still enjoyable to use. If you're interested in more advanced variations of shift ciphers, check out our Vigenère cipher calculator.

You can try it yourself using our free Caesar cipher shifter, an online tool that lets you encode or decode Caesar-encrypted text in seconds. Whether you're looking for a Caesar cipher encoder, a decoder, or want to translate Caesar cipher messages just for fun, you're in the right place.

As we mentioned, the Caesar shift cipher works by shifting each letter in a message by a $n$ fixed number of positions in the alphabet, where $n$ is an integer.

We can assign a number to each letter of the alphabet, e.g., in the Latin alphabet:

$A = 0, B = 1, C = 2, ..., Z = 25$

For encryption, each letter is shifted $n$ places forward in the alphabet. When the end of the alphabet is reached, it wraps around to the beginning.

To decrypt the message, we shift each letter $n$ places backward, reversing the process.

Then, we can apply the encoding formula for the Caesar shift cipher:

where:

• $C_i$ — Ciphertext letter number;
• $P_i$ — Plaintext letter number;
• $n$ — Number of positions each letter is shifted;
• $m$ — The number of letters in the chosen alphabet (e.g., $26$ in the Latin alphabet); and
• $\mathrm{mod}$ — Modulo operator.

The modulo operator ensures the result stays within the bounds of the alphabet by resetting to 0 after reaching $m$ — so if the shifted position goes beyond the last letter, it loops back to the start. You can explore how it works in our modulo calculator.

Let's take the Latin alphabet as an example: it has $26$ letters, from $A$ to $Z$. This means that after shifting past Z, we wrap back to A. Let's say you want to encrypt "SKY" with a shift of $5$:

We first gave each letter a number based on its place in the Latin alphabet, so $S$ becomes $18$ (with $A = 0$). Then we added $5$ to each number ($18 + 5 = 23$) and looked up which letter was at the new position. In this case, that's $X$. We simply repeat this process for each letter in your message, one at a time. If the result goes past the end of the alphabet, like $24 + 5 = 29$, we use modulo $26$ to wrap around, so $29$ becomes $3$, which corresponds to $D$. That gives us $X$, $P$, and $D$.

So, using Caesar's cipher with a shift of $5$, the word "SKY" becomes "XPD".

Let's try going the other way and decode a message using a Caesar cipher decoder. To decode a message encrypted with the Caesar shift cipher, we reverse the encoding process by subtracting the shift value $n$ from each letter.

Imagine a friend sends you a secret code: "GTC". Luckily, you also know the Caesar shift used was $5$.

Just like before, we start by assigning each letter ($G$, $T$, $C$) its position in the Latin alphabet, remembering that $A = 0$.

Then we subtract $5$ from each number and find the letter that corresponds to the new position:

So $G$ becomes $6$, $T$ is $19$, and $C$ is $2$.

Next, we subtract $5$ from each number. Most results stay positive, but look what happens with $C$: $2$ minus $5$ gives us $-3$, and we can't have negative positions. That's where modulo $26$ comes in. We wrap around the alphabet by adding $26$ to $-3$, giving us $23$, which means the letter $X$. That gives us the decoded message: "BOX".

Wondering how to decrypt a shift cipher without a key? Before algorithms and digital tools, people used a hands-on device to help with that: the Caesar wheel, or cipher disk. This tool consists of two rotatable rings with the alphabet printed on them. The outer ring stays fixed, while the inner ring rotates to apply the shift. To encode a message, you align the inner and outer rings based on your shift value.

Let's return to our examples. To encode the word "SKY" using a Caesar wheel with a shift of $5$, you rotate the inner ring so that A (position $0$) aligns with F (position $5$) on the outer ring. Then you find each letter of "SKY" (S, K, Y) on the inner ring and write down the letters directly above them on the outer ring, which gives you "XPD".

To decode a word like "GTC" with the same Caesar shift, you do the reverse: find each letter on the outer ring and read the one directly beneath it on the inner ring. That gives you "BOX". The Caesar wheel acts as both an encoder and a Caesar cipher decoder, making it a hands-on version of a Caesar cipher shifter that's easy and fun to use.

Modern Caesar wheels, whether physical or digital, are popular tools for learning how substitution ciphers work. In practice, you can solve a Caesar cipher either by rotating the wheel through all possible shifts for a given alphabet, e.g., $25$ in the Latin alphabet (brute-force method) or by comparing letter frequencies in the ciphertext to those typical for a given alphabet (frequency analysis). Today, Caesar wheels are still popular in classrooms, escape rooms, and online tools like Caesar cipher shifters, offering a tangible, hands-on way to explore the roots of encryption.

Using our Caesar cipher shifter is a quick and easy way to encode or decode messages without doing the math by hand. Here's how it works:

1. Input your message, whether it's plaintext to encrypt or ciphertext to decode.
2. Select your alphabet. It's set to Latin by default, but you can also choose Cyrillic, Greek, Hebrew, or Arabic.
3. Choose your shift value. This is the number of positions each letter will move in the alphabet.
4. Select the mode: pick encoding (to use the Caesar cipher encoder) or decoding (to use the Caesar cipher decoder).
5. Get your result. Our tool will automatically translate the Caesar cipher using your settings.