ROT13 ("rotate by 13 places") is a simple letter substitution cipher. Each letter is replaced by the letter 13 positions after it in the alphabet, wrapping around at Z. Because the English alphabet has 26 letters, applying ROT13 twice always returns the original text.

ROT13 provides no cryptographic security. It is used to obscure text (spoilers, puzzle answers, offensive content) so that casual readers do not see it accidentally - not to protect secrets.

How is ROT13 different from a Caesar cipher?

ROT13 is a Caesar cipher with a fixed shift of 13. Unlike a general Caesar cipher where you choose any shift from 1–25, ROT13 always uses 13 and is therefore self-inverse.

Are numbers and symbols affected?

No. ROT13 only transforms the 26 letters of the English alphabet (a–z, A–Z). Digits, punctuation, and other characters pass through unchanged.

ROT13 Encoder / Decoder

What is ROT13?

ROT13 ("rotate by 13 places") is a simple letter-substitution cipher that replaces each letter with the letter 13 positions after it in the alphabet. It is a special case of the Caesar cipher. Because the English alphabet has 26 letters, rotating by 13 twice brings you back to the start, so the same operation encodes and decodes.

What is ROT13 used for?

ROT13 is typically used to casually obscure text so that it cannot be read at a glance. Common uses include hiding puzzle answers, game spoilers, or mildly offensive jokes in forums and comment sections. It was historically popular on Usenet. It provides absolutely no cryptographic security.

ROT13 examples

Hello, World! -> Uryyb, Jbeyq!
The Quick Brown Fox -> Gur Dhvpx Oebja Sbk
Applying ROT13 again restores the original text.

ROT13 vs. Caesar cipher

ROT13 is a Caesar cipher locked to shift 13. A general Caesar cipher lets you choose any shift from 1 to 25, making it slightly harder to decode without knowing the key (though still trivial to break by brute force).

ROT13 alphabet table

Each letter maps to the letter 13 positions away. Because the alphabet has 26 letters, the mapping is its own inverse - encoding and decoding are identical operations.

Plain	A	B	C	D	E	F	G	H	I	J	K	L	M
ROT13	N	O	P	Q	R	S	T	U	V	W	X	Y	Z

Plain	N	O	P	Q	R	S	T	U	V	W	X	Y	Z
ROT13	A	B	C	D	E	F	G	H	I	J	K	L	M

ROT47

ROT47 is a variant of ROT13 that extends rotation to all 94 printable ASCII characters (codes 33–126, from ! to ~), rotating each by 47. Like ROT13, applying ROT47 twice restores the original text. ROT47 is useful when you need to obscure text that contains numbers, punctuation, or symbols in addition to letters - for example, code snippets or ASCII art where ROT13's letter-only rotation would leave non-alphabetic characters visible.