# Caesar Cipher > Encode and decode the Caesar shift cipher with any shift from 1 to 25, or crack a message without the key: every shift is tried and ranked for you. - Page: https://linguaholic.com/tools/caesar-cipher/ - Type: free online tool (Converters & translators), no sign-up, runs in the browser - Publisher: Linguaholic (https://linguaholic.com/), made by Marcel Iseli - Last updated: October 3, 2026 - Open it pre-filled: https://linguaholic.com/tools/caesar-cipher/?text=Khoor+Zruog&mode=decode&open=crack - `text`: text to encode or decode (for example `Khoor Zruog`) - `mode`: direction: encode (default) or decode (for example `decode`) - `shift`: number of places to shift, 1-25 (clamped); default 3 (for example `3`) - `open`: open a section: crack (try every shift), steps (cipher wheel and worked steps), frequency (letter counts) or identify (which cipher is this?) (for example `crack`) ## What is the Caesar cipher? The **Caesar cipher** (also called the **Caesar shift** or shift cipher) replaces every letter with the letter a fixed number of places further along the alphabet. With a shift of 3, A becomes D, B becomes E and C becomes F. At the end of the alphabet you wrap around to the start, so X becomes A, Y becomes B and Z becomes C. To read the message again you shift every letter back by the same number. The number of places, from 1 to 25, is the whole key. It is the simplest substitution cipher there is, which makes it the classic first step into codes: escape rooms, treasure hunts, classroom puzzles and geocaches use it all the time. It is also very easy to break, and this tool shows you how. ## How to use the Caesar cipher decoder and encoder 1. Choose **Encode** to hide a message or **Decode** to read one. 2. Set the **shift** with the − and + buttons or type a number from 1 to 25. The default, 3, is the shift the cipher is famous for. 3. Type or paste your text. The result appears as you type; capital and small letters stay as they are, and spaces, digits and punctuation pass through unchanged. 4. **Copy** the result, or press **Decode this** to send it back through the other way and check it. Below the result are four sections you can open: - **Crack it: I don’t know the key** tries all 25 shifts and ranks them by how much the result looks like English, using letter patterns and our dictionary. The right answer is almost always at the top. Press **Use shift** to apply it. - **Step by step** draws a cipher wheel turned to your shift, the plain and cipher alphabets lined up, and the arithmetic for the first letters of your text. - **Letter frequencies** counts the letters in your text and puts them next to typical English, the method code breakers use on longer messages. - **Which cipher is this?** guesses what kind of code a message uses, if you are not sure it is a Caesar shift at all. You can also open the tool already filled in from a link: `?text=Khoor&mode=decode&shift=3` decodes a message straight away, and `&open=crack` opens the cracker. ## Frequently asked questions **What is the Caesar cipher?** The Caesar cipher replaces every letter with the letter a fixed number of places further along the alphabet, wrapping from Z back to A. With a shift of 3, A becomes D and HELLO becomes KHOOR. **How do I decode a Caesar cipher?** Shift every letter back by the same number used to encode it. In the tool, choose Decode, set the shift and paste the message. If you do not know the shift, open Crack it: the tool tries all 25 shifts and puts the one that reads as English at the top. **How do you solve a Caesar cipher without the key?** Try all 25 shifts and keep the one that gives real words, or count the letters and assume the most common one stands for E. With a sentence or more, only one shift reads as English. **What shift did Julius Caesar use?** According to the Roman historian Suetonius, Caesar used a shift of three, so that D stood for A. That is why 3 is the default shift. **How many keys does a Caesar cipher have?** Only 25 useful ones, the shifts 1 to 25. A shift of 26 (or 0) leaves the text unchanged. That tiny number is why the cipher is so easy to break. **What is the difference between the Caesar cipher and ROT13?** ROT13 is a Caesar cipher with a fixed shift of 13. Because 13 is half of 26, applying it twice gives back the original, so the same step encodes and decodes. **What is a Caesar cipher wheel?** Two alphabet rings, one inside the other, that turn. Line up the inner ring at your shift and every plain letter on the outside sits next to its cipher letter. The Step by step section of the tool draws one for any shift. **Does the Caesar cipher change numbers and punctuation?** No. Only the 26 letters A to Z are shifted. Digits, spaces and punctuation stay as they are, and capital and small letters keep their case. **Is the Caesar cipher a substitution cipher?** Yes. It is the simplest kind of substitution cipher: each letter is always replaced by the same other letter, and the replacement alphabet is just the normal alphabet moved along. **Is my text private?** Yes. The tool runs entirely in your browser and nothing you type is uploaded or stored. ## Data sources The code breaker's English letter frequencies and word checks come from Linguaholic’s English dictionary, built from the open ENABLE and SCOWL word lists. Licenses and notices: https://linguaholic.com/tools/data/dict/v1/NOTICE.txt ## Related tools - [ROT13](https://linguaholic.com/tools/rot13/): Decode and encode ROT13 instantly (the same step does both), switch to ROT5, ROT18 or ROT47, or try every rotation when it is not ROT13. - [Vigenère Cipher](https://linguaholic.com/tools/vigenere-cipher/): Encode and decode the Vigenère cipher with a keyword, or crack a message without the key: the tool finds the key length and the keyword for you. - [Atbash Cipher](https://linguaholic.com/tools/atbash-cipher/): Encode and decode the Atbash cipher, which swaps each letter with its mirror (A↔Z, B↔Y), with the alphabet chart, step-by-step working and examples. - [Affine Cipher](https://linguaholic.com/tools/affine-cipher/): Encode and decode the affine cipher with keys a and b, see the arithmetic for every letter, or crack a message by trying all 312 keys. - [Substitution Cipher](https://linguaholic.com/tools/substitution-cipher/): Encode and decode with any cipher alphabet or keyword, or paste a cryptogram and let the solver crack it; then fix any letter yourself. - [Morse Code Translator](https://linguaholic.com/tools/morse-code-translator/): Translate text to Morse code and decode it back, hear it as adjustable-speed sound with a visual flasher, and read the full Morse alphabet, number, and punctuation chart.