Secret Codes
Classic ciphers for puzzles, games, and secret messages — encode and decode entirely in your browser.
A playful corner of the toolkit dedicated to classic cryptography. Encode notes for an escape-room puzzle, build a code-breaking lesson for the classroom, or send a message your kid sister can't read over your shoulder. Every tool runs entirely in your browser — your message never leaves your device, no signup, no servers.
What's Inside
- Caesar Cipher — shift every letter by a fixed amount (the simplest classic cipher, used by Julius Caesar himself).
- Keyword Cipher (Vigenère) — use a secret keyword to vary the shift letter-by-letter. Far stronger than a Caesar shift and famously called le chiffre indéchiffrable (the indecipherable cipher) for nearly 300 years.
Caesar Cipher
Shift every letter by 1–25 places to encode or decode a message. Includes the famous ROT13 mode used in online forums for spoiler text.
Keyword Cipher (Vigenère)
Pick a secret keyword and the cipher rotates through it letter-by-letter as it encodes your message. Stronger than Caesar — and great fun for puzzles and games.
Common Use Cases
- Build escape-room or scavenger-hunt clues that need decoding
- Teach kids and students about classic cryptography and code-breaking
- Write spoiler-safe text for forums, fan wikis, or message boards (ROT13)
- Add atmospheric "encrypted note" props to TTRPG campaigns and LARPs
- Solve cipher-based puzzles in books, video games, or ARGs
A Note on Security
Caesar and Vigenère ciphers are fun, not secure. They are easily broken by modern frequency-analysis tools and should never be used to protect real secrets. For genuine encryption (passwords, financial data, private files), use a modern algorithm like AES via a trusted password manager or encrypted messenger. These tools exist for puzzles, games, and learning the history of cryptography.