ROT13 & Caesar Cipher
Encode and decode text with ROT13 or a custom Caesar cipher shift.
The Caesar cipher — shifting every letter a fixed number of places down the alphabet — is the oldest encryption trick in the book, famously used by Julius Caesar himself. ROT13 is its most popular modern form: a shift of 13 that's its own inverse, so the same operation both hides and reveals text. It's used to mask spoilers, puzzle answers and joke punchlines online, and it's the classic first lesson in cryptography.
Type text and pick a shift (13 for ROT13, or any value) to encode or decode. Because ROT13 applied twice returns the original, one button handles both directions. Letters shift; numbers, spaces and punctuation pass through unchanged.
How to use ROT13 & Caesar Cipher
- 1
Enter your text
Plain text to encode, or ROT13 text to decode.
- 2
Choose a shift
13 for classic ROT13, or any 1–25 shift.
- 3
Copy the result
Same operation decodes ROT13 back to plain text.
Features
- ROT13 and custom Caesar shifts
- Self-inverse ROT13 for one-click decode
- Preserves numbers, spaces and punctuation
Frequently asked questions
Common mistakes to avoid
- Using ROT13 or Caesar ciphers to protect sensitive data — they're not secure.
- Expecting numbers to shift — classical Caesar ciphers only rotate letters.
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