Caesar Cipher — Encrypt and Decrypt Text Online
Caesar cipher online: encrypt or decrypt text by shifting letters. Latin and Cyrillic, any shift, and a brute-force view of every variant when the key is unknown.
The shift is the key: how many letters each one moves. The classic Caesar shift is 3.
Result
Don't know the shift?
We run through every shift and show each result — you just spot the readable one. The number on the left puts that shift into the field above.
About the Caesar cipher
The Caesar cipher moves every letter the same number of positions along the alphabet: with a shift of 3, A becomes D and B becomes E. When it runs past the end of the alphabet it wraps around to the beginning. Digits, spaces and punctuation stay as they are, and letter case is preserved.
Cyrillic text is handled with the full 33-letter alphabet including “ё”. That matters when decrypting someone else's message: if it was encrypted with a 32-letter alphabet without “ё”, the result is off by one position and reads as nonsense. Checking every variant solves it — the right line will be next to the wrong one.
The cipher is named after Julius Caesar, who used it for military correspondence. Today it is not protection but a teaching example: there are only 32 possible keys and they can be tried in seconds — which is exactly what the button does. Everything runs in your browser and no text is sent anywhere.
When it comes in handy
Computer science homework
Check your own answer or see how the shift works on a concrete example.
Decrypt a message
If you don't know the key, press “Show every variant” — the readable line stands out among the rest.
Escape room or game
Encrypt a hint for a quest, a note or a board game and let players work out the shift.
Learning cryptography
The Caesar cipher is the simplest substitution cipher and the usual starting point for studying encryption.
Frequently asked questions
How do I decrypt a Caesar cipher without the key?
Press “Show every variant”. The tool runs through all possible shifts and lists every result, so you can spot the readable one by eye. The numbered button on the left drops that shift into the field above.
What shift did Caesar himself use?
Three. According to Suetonius, Julius Caesar moved each letter three positions forward, which is why a shift of 3 is considered the classic form of the cipher. It is the default here.
Is the letter “ё” included?
Yes, the full 33-letter Cyrillic alphabet is used. Some services work with 32 letters and omit “ё”, so their output differs by one position. If a decryption looks like nonsense, check the neighbouring shifts in the list of variants.
Can I encrypt Latin and Cyrillic text together?
Yes. Each letter is shifted within its own alphabet — Cyrillic along the Cyrillic one, Latin along the Latin one. Mixed text is handled in a single pass, and digits and punctuation are left as they are.
How secure is the Caesar cipher?
Not secure at all, and that is a property of the cipher rather than a flaw in the tool. There are only a few dozen keys and they can be tried instantly — which is what the “Show every variant” button does. It is useful for learning and games, not for protecting real data.
Is my text sent to a server?
No. Encryption and decryption happen in your browser on your own device — the text you type is never transmitted or stored anywhere.