ROT13 is a Caesar cipher that rotates each letter 13 places through the 26-letter alphabet. A becomes N, B becomes O, and so on. It is used to hide spoilers and puzzle answers, not for real security.

Why does applying ROT13 twice do nothing?

Rotating 13 places and then another 13 places is a total rotation of 26 places, which is one full trip around the alphabet back to the starting letter. So two ROT13 passes return the original text exactly.

Is ROT26 a real encryption method?

No. ROT26 is a running joke in cryptography circles precisely because it is the identity function — it transforms nothing. It is used to illustrate that adding rounds of a self-inverse operation gives no extra protection.

What happens to numbers and punctuation?

Only the 26 ASCII letters are rotated. Digits, spaces, punctuation, and any non-Latin characters pass through unchanged in both passes, just as standard ROT13 leaves them alone.

Can I use this to decode ROT13 text?

Yes. Because ROT13 is self-inverse, the single-pass output of this tool decodes ROT13-encoded text. Paste the encoded text and read the value after one pass.

Double ROT13 (ROT26)

Double ROT13 — affectionately called ROT26 — is the classic cryptography joke: it runs the ROT13 cipher twice and gives you back exactly what you started with. This tool demonstrates that self-inverse property step by step.

How it works

ROT13 rotates each letter 13 positions forward, wrapping around at the end of the alphabet:

encrypted = ((letter - base + 13) mod 26) + base

Apply it a second time and the total shift is 13 + 13 = 26, a full rotation around the 26-letter alphabet:

(x + 13 + 13) mod 26  =  (x + 26) mod 26  =  x

So the second pass perfectly undoes the first. The tool shows the intermediate single-pass result, then the double-pass result, which always equals the input.

Tips and notes

Because ROT13 is its own inverse, the same operation both encodes and decodes — there is no separate decode mode in plain ROT13.
Only letters move; everything else is left untouched, which is why the joke works on any text including symbols and digits.
The takeaway: stacking rounds of a self-inverse transform adds no security. Real ciphers avoid this by mixing different, non-cancelling operations.