Caesar Cipher

Written byOleh Soloninupdated 25 September 2026

Text

Shift

Operation

Result

ResultТулезх, XqlWrrov
ROT13Привет, HavGbbyf
Reverse transformПривет, UniTools
Shift applied3
Letters in the text14

The cipher everyone meets at school

Shift cipher for the Latin and Cyrillic alphabets, with ROT13 shown separately and the reverse transform for checking.

The Caesar cipher shifts every letter a fixed number of places along the alphabet. Julius Caesar, according to Suetonius, used a shift of three — hence the name. By modern standards it is a puzzle rather than encryption.

Breaking it is trivial: there are only as many possibilities as letters in the alphabet, and checking them by hand takes a minute. Frequency analysis is often faster: in a long enough English text the commonest letter is usually E, which suggests the shift. In a short message it may not be, so confirm by trying the shifts.

How to use

Type the text — English, Russian or a mix.
Choose encode, decode with a known shift, or try every shift.
Set the shift and copy the result; below it you get ROT13 for Latin letters and a reverse check.

One line, four shifts

Latin letters wrap around a 26-letter circle and Cyrillic around 33 letters including ё. Case, spaces and punctuation stay put.

Every row is output from this page's cipher.
Shift	'Привет, UniTools' encoded
1	Рсйгёу, VojUppmt
3	Тулезх, XqlWrrov
13	Ьэхося, HavGbbyf
25	Зибъэк, TmhSnnkr

What this calculator shows

The encoded or decoded text
ROT13, the shift of thirteen that is its own inverse in Latin
The reverse transform, so the result can be checked immediately

What to keep in mind

Latin and Cyrillic alphabets are supported; case is preserved and punctuation and digits pass through untouched.
Cyrillic counts ё as its own letter, giving 33 positions.

FAQs

What is ROT13?

A Caesar cipher with a shift of 13. Because the Latin alphabet has 26 letters, applying it twice returns the original. Usenet used it to hide spoilers from a passing glance.

How do I break a Caesar cipher without the key?

Try every shift: 25 for the Latin alphabet, 32 for Russian with ё. Pick 'decode without a key — all shifts' and look for the line that reads: for 'XqlWrrov' it is shift 3 — 'UniTools'.

Can it protect anything?

No. It is a teaching example and a puzzle. Real protection needs modern algorithms, and passing secrets needs an end-to-end encrypted messenger.

Why is the Vigenère cipher stronger?

Its shift changes from letter to letter according to a keyword, so frequency analysis does not work directly. It was considered unbreakable for about three hundred years, until Kasiski published a method in 1863.

Why doesn't a shift of 13 undo itself for Cyrillic?

The Russian alphabet has 33 letters, so applying 13 twice gives a shift of 26, not a full circle. Only an alphabet with an even number of letters has a self-inverse shift.

Do punctuation and digits change?

No. Only letters move; spaces, punctuation and digits stay exactly where they were, which is also why the cipher is so easy to break.

Worked example

A shift of three

Input: Привет, UniTools shifted by 3

Output: Тулезх, XqlWrrov

Note: Punctuation and spaces stay put, which is exactly why the cipher is so easy to break: the structure of the text survives intact.

Useful links

All tools in Text tools for word count, character count, and quick cleanup

Caesar Cipher

Result

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