ROT13 Encoder & Decoder

ROT13 ('rotate by 13 places') is a simple letter-substitution cipher, a specific case of the Caesar cipher with a fixed shift of 13. Each of the 26 letters is replaced by the letter 13 positions later in the alphabet, wrapping around from Z back to A: A becomes N, B becomes O, and so on. Because 13 is exactly half of 26, applying the transformation a second time shifts each letter another 13 positions and lands back on the original letter, which makes ROT13 self-inverse: a single function both encodes and decodes. This tool implements ROT13 on the basic Latin alphabet only. It shifts uppercase A to Z and lowercase a to z while preserving case, and it leaves everything else untouched: digits, spaces, punctuation, line breaks, and any accented or non-Latin characters pass through unchanged. ROT13 has roots in Usenet culture, where it was a convention for hiding spoilers, puzzle answers, and offensive jokes so readers had to deliberately decode them. It offers no cryptographic security whatsoever; the key is fixed and public, so anyone can reverse it instantly. Think of it as light obfuscation or a reversible scrambling trick, not encryption.