Caesar Cipher

Shift each letter by a fixed number of steps around the alphabet.

Difficulty: Beginner

How it works

  1. Choose a shift value between 0 and 25. A shift of 3, for example, means A → D, B → E, C → F and so on.
  2. Write your message using letters and spaces. Numbers and punctuation can be left as they are.
  3. To encrypt, move each letter forward in the alphabet by the shift amount, wrapping around after Z (so X→A for shift 3).
  4. To decrypt, move letters backwards by the same shift. If you encrypted with +3, you decrypt with −3.
  5. Try simple experiments: see what happens when you shift by 0, 13 (ROT13) or 25, and notice how patterns in the message stay visible.
Press Shift + Enter

What is it?

The Caesar Cipher is one of the earliest known and simplest ciphers. It is a type of substitution cipher in which each letter in the plaintext is shifted a certain number of places down the alphabet. Named after Julius Caesar, who used it with a shift of three to protect messages of military significance, it is mathematically represented as a simple addition modulo 26. While practically useless for security in the modern era due to its vulnerability to brute-force and frequency analysis attacks, it serves as the foundational stepping stone for understanding cryptographic principles and modular arithmetic.

Try it yourself

Manual Solver

Can you decrypt this challenge?

JYFWAVNYHWOF PZ MBU (Hint: Shift = 7)
Plaintext
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Z
Ciphertext
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Z
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Z

Where this shows up today

To communicate securely with his generals during military campaigns.