ROT13 / Caesar Cipher

13 (ROT13)

Why Use a Caesar Cipher?

The Caesar cipher is the oldest known substitution cipher — each letter is shifted a fixed number of places through the alphabet, wrapping around at the end. A shift of 13 is the well-known ROT13 scheme, long used on forums and newsgroups to hide spoilers and punchlines from casual glances. Digits, punctuation, and spacing are left untouched, and letter case is preserved.

Features

  • Adjustable shift — any amount from 1 to 25, not just the classic ROT13.
  • Case preserved — uppercase and lowercase letters shift independently.
  • Non-letters untouched — digits, punctuation, and spacing pass through unchanged.
  • Symmetric operation — apply the same shift again (mod 26) to reverse it.
  • Copy to clipboard — grab the result with one click.

Common Use Cases

  • Hiding spoilers, puzzle answers, or punchlines in forum posts.
  • Simple obfuscation for alternate reality games (ARGs) and puzzle hunts.
  • Learning how classical substitution ciphers work before studying modern cryptography.

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