Encoding
ROT13 / Caesar Cipher
Caesar cipher — a cyclic shift of Latin alphabet letters. ROT13 is the special case with shift 13 (button below), symmetric: encode and decode give the same result. Other characters (digits, punctuation, non-Latin letters) are left unchanged.
A Caesar cipher cyclically shifts every letter of the alphabet by a fixed number of positions. ROT13 is the special case with a shift of 13, which makes the cipher self-inverting: apply ROT13 twice and you get the original text back.
How to use it
- For ROT13, just paste text — encoding and decoding are the exact same operation.
- For a custom Caesar shift, specify how many positions to shift (1-25).
- Digits, punctuation, and non-Latin characters are left unchanged.
Common uses
- Hiding a spoiler or answer in a forum post so it isn't read accidentally at a glance.
- A historical or teaching example of the simplest substitution cipher when learning cryptography.
- Light obfuscation of text in code or a config where cryptographic strength isn't needed.
Things to keep in mind
ROT13 is not encryption in any security sense — it's obfuscation, trivially broken by hand without any tool or key.
Since the Latin alphabet has 26 letters and 13 is exactly half of that, ROT13 is symmetric: the same operation encodes and decodes.
Article about this tool: ROT13 and the Caesar cipher: simple character substitution
Frequently asked questions
Is ROT13 actually secure?
No, not at all. ROT13 is a trivial letter-rotation cipher with no real security — anyone can decode it instantly, even by eye. It's used for obfuscating spoilers or puzzle answers, not for protecting sensitive data.
Why does encoding and decoding give the same result for ROT13?
ROT13 shifts letters by 13, exactly half of the 26-letter alphabet, so applying it twice returns the original text — encode and decode are the same operation.
What happens to numbers, punctuation, or non-Latin letters?
They're left unchanged. Only Latin alphabet letters are shifted; the custom shift value works the same way for any Caesar cipher variant.
How is ROT47 different from ROT13?
ROT47 works over a wider ASCII range (33–126), so it also shifts digits, punctuation, and special characters, not just Latin letters, while keeping the same self-inverse shift idea.
Can ROT13 be cracked without a tool?
Yes, easily — just read the text while mentally shifting each letter by 13 positions, or remember that A↔N, B↔O, and so on through the alphabet. It's not protection, just light obfuscation.