buttcrack. Cipher Wiki

ROT13

From the Buttcrack Cipher Wiki — the free field guide to classical ciphers

ROT13 — A Caesar shift of thirteen. Because thirteen is half of twenty-six, encryption and decryption are the same operation.

Caesar shift of 13. Applying it twice returns the original text.

A worked example§

Encrypting a sample with the cipher itself, at build time:

MEET ME BY THE OLD CLOCK TOWER AT DAWN

No key — the transformation is fixed.

produces the ciphertext

ZRRG ZR OL GUR BYQ PYBPX GBJRE NG QNJA

This example is generated by running the cipher when the page is built, and the round trip is checked, so it always matches what the solver does.

How it is broken§

There is no key to find. Apply it and read.

History and context§

A Usenet convention from the early 1980s for hiding punchlines and spoilers — politeness rather than secrecy, and still used that way.

See also§

Caesar (ROT-N) · Atbash · Affine · ROT47 · Reverse

Browse every cipher in the Shift and reciprocal alphabets family, read the history of codebreaking, or return to the wiki main page.

Frequently asked questions§

How is the ROT13 broken?

There is no key to find. Apply it and read.

What key does the ROT13 use?

none (fixed shift of 13). There are 1 possible keys.

How much ciphertext do I need?

At least 2 characters for this solver to attempt it; short messages can be readable and still not be proof.

Can I break a ROT13 on this page?

Yes — the browser solver on this page handles it directly. Paste the ciphertext into the solver and press the button.

Categories: Shift and reciprocal alphabets | Breakable in the browser | Cipher wiki
The facts in this article are generated from buttcrack's cipher registry when the site is built, so they describe the implementation you can run on this page. Registry-generated content is checked against the code; the history is editorial.

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What this browser solver can—and cannot—do

It tries: Caesar, Atbash, ROT13, affine, Trithemius, rail fence, single-byte XOR, periodic Vigenère-family ciphers, autokey, selected encoding layers (such as Base64, hex, binary, decimal ASCII, Morse, and reverse), and—only with 60+ A–Z letters—statistical substitution.

It does not: prove a decryption, cover every classical cipher, or break modern encryption such as AES or RSA. Its ranking model is tuned for English, so a high score is a lead to verify with the method, key, and source context—not a guarantee.

Short text, non-English plaintext, non-Latin or symbol alphabets, missing keys, and unsupported formats can all leave no high-confidence answer. When that happens, the result includes input-specific observations and suggested next checks; those observations are not a claim to know the exact cause.

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