Text & Writing Tools
Caesar Cipher & ROT13 Tool
Encode and decode Caesar shift ciphers, including ROT13, with automatic cracking.
Privacy
Everything runs inside your browser. Nothing you type or paste is transmitted, logged or stored — which matters for drafts, credentials and anything not yet public.
Tips
- ROT13 is a Caesar cipher with a shift of 13. Because the alphabet has 26 letters, applying it twice restores the original.
- "Try every shift" scores all 26 possibilities against English letter frequencies and marks the most likely with a star.
- This is not encryption. A Caesar cipher has 25 possible keys and is broken instantly — it is a puzzle and a teaching tool, nothing more.
- Non-letters pass through unchanged, so punctuation and spacing survive the round trip.
Frequently asked questions
Can I use this to protect something?
No. Anyone can break a Caesar cipher by hand in under a minute, which this tool demonstrates. Use real encryption for anything that matters.