Caesar Cipher / ROT13 Tool
Encode or decode text with a Caesar shift cipher, including the classic ROT13.
ROT13 is just a Caesar cipher with a shift of 13 — applying it twice gets you back the original text. Everything runs in your browser.
Frequently asked questions
What is a Caesar cipher?+
One of the oldest known ciphers — each letter is shifted a fixed number of places through the alphabet (wrapping from Z back to A). Numbers, spaces, and punctuation are left unchanged.
What makes ROT13 special?+
ROT13 is a Caesar cipher with a shift of exactly 13 — since the alphabet has 26 letters, applying the same ROT13 transformation twice returns the original text.
Is this secure encryption?+
No — a Caesar cipher is trivially easy to break and offers no real security. It's meant for puzzles, obscuring spoilers, or as a teaching example, not protecting sensitive information.
Related tools
Case Converter
Convert text to UPPERCASE, lowercase, Sentence case, Title Case, aLtErNaTiNg case, and more.
Code Case
Convert identifiers between camelCase, PascalCase, snake_case, kebab-case, and CONSTANT_CASE.
Slugify
Turn any text into a clean, URL-safe slug.
Word Counter
Count words, characters, sentences, and paragraphs, plus see your most frequent words.