ROT13 / ROT47 / Atbash Cipher

Apply classic substitution ciphers: ROT13 (Caesar +13 on letters), ROT47 (Caesar +47 on all printable ASCII), ROT5 (Caesar +5 on digits), or Atbash (mirror the alphabet). All are involutions — applying twice returns the original — so the same tool encodes and decodes. Useful for puzzles, mild content obfuscation (Usenet-style spoiler protection), or learning how substitution ciphers work.

How to use the ROT13 / ROT47 / Atbash Cipher

Pick a cipher. The output updates as you type. ROT13 and Atbash are self-inverse: encrypt twice and you're back to the original. ROT47 covers a wider character range (all printable ASCII), useful when you need to obscure punctuation and digits too. Custom Caesar shift lets you pick any rotation (positive = forward, negative = backward).

What is the ROT13 / ROT47 / Atbash Cipher?

Classical substitution ciphers map each character to another according to a fixed rule. ROT13 (and its cousins) are weakest possible encryption — anyone who knows the cipher can decode trivially — but that's the point. They're used for spoiler protection, mild content warnings, and puzzles where the goal isn't secrecy but a small barrier to casual reading.

Atbash is the oldest known substitution cipher, originating in Hebrew scribal tradition (the name comes from the first/last/second/second-last Hebrew letters). ROT47 was popularised on Usenet in the 1990s as a fairer ROT13 for non-English text.