🗝️ Online Cipher Tool
Free online encoder and decoder: Caesar, Vigenère, Atbash, ROT13, affine cipher, Morse code, Base64 and more. Supports Latin and Cyrillic. Runs in your browser, no sign-up.
Enter text
Cipher
Result
Enter text…
Online Cipher Tool
Free online encoder and decoder: Caesar, Vigenère, Atbash, ROT13, affine cipher, Morse code, Base64 and more. Supports Latin and Cyrillic. Runs in your browser, no sign-up.
Cipher
Caesar Cipher
Each letter is shifted N positions along the alphabet. The classic cipher of Julius Caesar (shift 3), with a brute-force view of all shifts.
hello → khoor
ROT13
Caesar with shift 13 for Latin letters. The alphabet has 26 letters, so encrypting and decrypting are the same operation.
Hello → Uryyb
ROT47
Extended ROT13: rotates all 94 visible ASCII characters — letters, digits and punctuation — by 47.
Hello → w6==@
Atbash
The alphabet is mirrored: the first letter becomes the last, the second the second-to-last. No key needed.
hello → svool
Vigenère Cipher
A polyalphabetic cipher: each letter is shifted by the value of the matching letter of a repeating keyword. Stronger than Caesar.
hello → rijvs
Affine Cipher
Letter x becomes (a·x + b) mod n, where a must be coprime with the alphabet length. A generalization of Caesar.
hello → rclla
Rail Fence
A transposition cipher: text is written in a zigzag over N rails and read row by row. Letters are only rearranged.
HELLO WORLD → HOREL OLLWD
A1Z26
Every letter is replaced by its position in the alphabet: A=1, B=2… The simplest numeric cipher for puzzles.
hello → 8-5-12-12-15
Morse Code
Dots and dashes. Letters are separated by spaces, words by a slash /. Tables for Ukrainian, Russian and English.
hello → .... . .-.. .-.. ---
Base64
Encodes text (UTF-8) into 64 printable characters. Not encryption, but common in APIs, tokens and e-mail.
Hello → SGVsbG8=
Binary Code
Every byte of the text as 8 bits. In UTF-8 a Cyrillic letter takes 2 bytes.
Hi → 01001000 01101001
Hex
Every byte of the text in hexadecimal. Handy for debugging and data analysis.
Hi → 48 69
When to use
- Studying and computer-science contests
- Puzzles, quests and games
- Hiding spoilers or answers (ROT13, Atbash)
- Encoding data: Base64, Hex, binary
How to use
- Pick a cipher
- Choose Encrypt or Decrypt
- Type your text and set the shift or key
- The result updates instantly — press “Copy”
FAQ
What is the Caesar cipher?
It is one of the oldest substitution ciphers. Every letter is shifted by a fixed number of positions in the alphabet; with shift 3, A becomes D. Decryption shifts back.
How do I decode a Caesar cipher with an unknown shift?
Select the Caesar cipher and press “Try all shifts”. The tool lists the result for every shift so you can spot the readable one.
Which alphabets are supported?
English letters are recognized automatically; no alphabet selection is needed. Every letter is shifted within its own alphabet, while digits, spaces, punctuation and other characters stay unchanged. Letter case is preserved.
How does the Vigenère cipher differ from Caesar?
With Caesar the shift is the same for the whole text; with Vigenère each letter is shifted by an amount set by the corresponding letter of the keyword. This spreads out letter frequencies, making the cipher harder to break.
Why are encoding and decoding identical for ROT13 and Atbash?
These are symmetric transformations: applying them twice returns the original text. ROT13 shifts the Latin alphabet by 13 of 26 letters, and Atbash mirrors the alphabet.
Why doesn't the Affine cipher accept certain values of a?
The number a must be coprime with the alphabet length, otherwise different letters would map to the same ciphertext and decoding would be impossible. The tool will tell you if a chosen value of a doesn't work.
Are these ciphers secure?
No. They are historical and educational and easy to break. Base64, binary and Hex are encodings, not encryption. Use modern algorithms such as AES for real protection.
Is my text sent to a server?
No. Everything runs in your browser and your text never leaves it.