Caesar Cipher
Use the CaseSwitch Caesar Cipher to shift letters by N places (HELLO with shift 3 → KHOOR). Choose Encode or Decode, set the shift, and copy the result. Processing stays in this browser — and this cipher is trivially breakable.
Written by the CaseSwitch editorial team. We maintain these tools in the browser so drafts, keys, and images stay on your device.
Last reviewed: 23 July 2026
Processed locally in your browser. Nothing is sent to a server.
Paste or type text to convert. Output stays empty until there is input.
Character count: 0 · Word count: 0 · Line count: 0
Examples
Encode HELLO (shift 3)
Input
HELLO
Output
KHOOR
Encode HELLO (shift 1)
Input
HELLO
Output
IFMMP
Decode KHOOR (shift 3)
Input
KHOOR
Output
HELLO
Preserve punctuation and case pattern
Input
Hello, World!
Output
Khoor, Zruog!
Encode abc (shift 5)
Input
abc
Output
fgh
How to use
- Set the shift (default 3) and choose Encode or Decode.
- Paste the text.
- Copy the result. Try shift 13 and compare with the ROT13 tool.
What this tool is for
The Caesar cipher rotates the alphabet by a fixed shift. Historical anecdotes say Julius Caesar used three; homework still uses it to teach frequency analysis. It must never protect passwords, tokens, or anything covered by a security policy.
How it works
Each A–Z / a–z letter rotates within its case by the shift you choose (default 3). Decode applies the inverse shift. Digits and punctuation stay unchanged. Unicode letters outside A–Z are not rotated as a “full Unicode Caesar.”
When to use it
Teaching frequency analysis, puzzle hunts, classroom demos, and explaining why real crypto uses modern algorithms and keys.
When not to use it
Passwords, API tokens, homework answers you think are secret, or anything adversarial. Prefer TLS and real libraries for confidentiality.
How it compares to related tools
ROT13 is Caesar with shift 13 (self-inverse). A1Z26 uses numbers. Base64 is not a cipher.
Common mistakes
Thinking a “weird” shift makes it strong. Shifting Unicode letters outside A–Z and expecting rotation. Using Caesar on passwords.
Why it is weak
There are only 25 nontrivial shifts. You can try them all by hand. Letter frequencies in English still show through. Treat every Caesar ciphertext as public.
Case and punctuation
Uppercase and lowercase rotate within their own ranges (`a→d`, `A→D` with shift 3). Spaces, digits, and punctuation stay put so phrases remain readable as puzzles.
Frequently asked questions
What shift did Caesar use?+
Historical anecdotes say three. This tool lets you pick any shift. Security is still zero.
Does it preserve case?+
Yes: letters keep upper/lower case while rotating. Digits and punctuation stay unchanged.
Is ROT13 a Caesar cipher?+
Yes — Caesar with shift 13. Use the ROT13 page when you specifically want that spoiler convention.
Can I decrypt without knowing the shift?+
For English, try all 25 shifts or use frequency analysis. That ease is why it is not security.
Does it shift emoji or accented letters?+
Only A–Z and a–z rotate. Other characters pass through unchanged.
Is my text uploaded?+
No. Conversion runs in this browser.
Does this tool send my payload to CaseSwitch?+
No. Formatting, encoding, and naming conversions for this page run in your browser after load — your sample stays on the device.
Related tools
ROT13 Encoder
Hiding movie endings in a forum post, classic Usenet-style spoilers, classroom demos of symmetric trivial ciphers, and quick round-trips to show self-inverse behavior.
A1Z26 Cipher
Worksheets, escape-room handouts, ARG puzzles, and explaining that “codes” are not all encryption.
Morse Code Translator
Study sheets, escape rooms, short callsign experiments, and demonstrating that “codes” are not all cryptography.