All possible Caesar cipher rotations of your input. Readable text will stand out.
| Shift | Output |
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ROT13 is a simple letter-substitution cipher that rotates every letter by 13 positions — making it its own inverse, so encoding and decoding are the same operation. The Caesar Cipher extends this idea to any shift from 1 to 25, letting you lock or unlock any message with a single click. Use this free online tool to instantly encode or decode text with no software to install and nothing ever sent to a server.
How to Use the ROT13 / Caesar Cipher Tool
- Paste or type your text into the input box on the left.
- Choose your cipher mode — select ROT13 for the classic 13-shift, or choose Caesar Cipher and set any shift value from 1 to 25.
- Click Encode or Decode (or just watch the output update live as you type).
- Copy the result with the one-click copy button, or download it as a
.txtfile. - Swap input and output using the flip button to run the cipher in reverse without re-typing.
Why Use Flipper File to Encode or Decode Ciphers?
- Instant live preview — output updates in real time as you type, no button press needed
- ROT13 and all 25 Caesar shifts — covers every rotation with a single slider or preset button
- Completely private — all processing happens in your browser; your text never leaves your device
- Decode mode included — both encode and decode in the same tool, with brute-force "show all shifts" option
- One-click copy — grab the result instantly without selecting text manually
- Free with no login — no account, no email, no file size limits
Frequently Asked Questions
What is ROT13?
ROT13 (Rotate by 13) is a Caesar cipher variant where every letter is shifted 13 positions in the alphabet. Because the English alphabet has 26 letters, applying ROT13 twice returns you to the original text — making it both the encode and the decode operation.
What is a Caesar Cipher?
A Caesar cipher is one of the oldest and simplest encryption techniques. It works by shifting each letter in the plaintext by a fixed number of positions down the alphabet. With a shift of 13 you get ROT13; with a shift of 3 you get the cipher Julius Caesar is said to have used.
Does ROT13 work on numbers and punctuation?
No — ROT13 and Caesar ciphers only affect letters (A–Z, a–z). Numbers, spaces, and punctuation pass through unchanged.
Is ROT13 encryption secure?
No. ROT13 is not secure encryption — it's trivially reversed by anyone who knows about it, and it's not intended for security. It's most commonly used to hide spoilers, puzzle answers, or mild content in forums and online communities.
What is "brute-force all shifts"?
This option outputs all 25 possible Caesar shift variants of your text at once, so you can quickly scan which rotation produces readable output when decoding an unknown cipher.
Can I decode a Caesar cipher if I don't know the shift?
Yes — use the "Show all shifts" / brute-force option. It displays all 25 possible rotations. Readable English will stand out immediately, making it easy to identify the correct shift without guessing.
Does this tool work on my phone?
Yes — the tool is fully mobile-responsive and works in any modern browser on Android or iOS.
Are there any limits on text length?
No. The tool works entirely in your browser and can handle text of any length — from a single word to a full document — without any file size restrictions.