Caesar Cipher / ROT13

Caesar Cipher and ROT13 Encoder / Decoder

The Caesar cipher is the simplest substitution cipher in cryptographic history — every letter is shifted forward by a fixed amount in the alphabet. ROT13 is the special case where the shift is exactly 13 (the same operation encodes and decodes). CipherForces Caesar Cipher tool encodes, decodes, and brute-forces shift ciphers entirely in your browser.

Three Modes

• Encode: Pick a shift (1–25, default 13 for ROT13) and the plaintext is shifted forward. Punctuation, numbers, and spaces are preserved.
• Decode: Same operation in reverse — given the ciphertext and the shift used, recover the plaintext.
• Brute-force: Don't know the shift? The tool prints all 25 possible decryptions in one column so you can eyeball which one reads as English. Useful for puzzle hunts and CTF challenges.

What Caesar Is — and Isn't — Good For

This is a classroom and puzzle-hunt cipher, not real cryptography. Twenty-five possible shifts are trivially brute-forced in a fraction of a second; even a frequency-analysis attack on a single sentence usually reveals the shift instantly. Do not use Caesar (or ROT13) to protect anything that matters. For real encryption use our Encrypt & Decrypt tool (AES-256).

Common Use Cases

• Puzzle hunts and ARGs: Caesar shifts are a common first-layer cipher. Brute-force mode solves them in one click.
• Spoiler text on forums and Reddit: ROT13 is the convention — readers who want to see the spoiler decode it deliberately.
• Teaching cryptography basics: The clearest possible illustration of substitution and why key space matters.
• Light obfuscation in code: Hide an easter-egg string in source so it doesn't grep cleanly.

Privacy

Pure JavaScript string transformation. Nothing leaves your browser. The "secret" of a Caesar cipher is the shift number, which is also trivial to discover — but at least our tool isn't logging your text either way.