buttcrack.

Automatic classical cryptanalysis

Puzzle Books.

Pencil-and-paper cryptograms, graded and solved, as printable PDFs.

Private by design

Drop in a puzzle. Leave with an answer.

Runs on this device
Try a sample
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.

No account. No upload. No stored text. The complete solver runs in your browser.

Printable cryptogram books

The solver on this site breaks ciphers. These books are the other direction: quiet, pencil-and-paper puzzles built from the same engine. Every quotation is a short fragment from a historical figure, every puzzle is graded, and every answer is in the back.

Free sampler

Ten puzzles from the collection, with solutions. No email, no checkout — just the file.

Download free PDF

The Cryptogram Collection, Volume One

60 hand-graded cryptograms, easy to hard, with a full solutions section. Print it or solve on screen.

60 puzzles · full solutions · PDF · 330 KB

Buy for $5

The Cryptogram Collection, Volume Two

90 more puzzles at a step up in difficulty, with Caesar rotations mixed in throughout.

90 puzzles · full solutions · PDF · 482 KB

Buy for $7

Payment is handled by Stripe. Files are delivered instantly in the browser after checkout — no account, no mailing list, no subscription.

What is inside

Each volume opens with a page on technique — how to attack one-letter words, why THE is the most valuable guess you can make, which doubled letters to expect — then works from puzzles with several letters given up to puzzles with nothing at all. Every fifth puzzle is a Caesar rotation for a change of pace.

They are typeset for US Letter with answer blanks under every character, so they print cleanly and are comfortable to work on directly.

Frequently asked questions

What format are the books in?

PDF, typeset for US Letter paper with answer blanks under every character. They print cleanly on a home printer and are equally usable on screen.

Do I need an account to buy one?

No. Checkout is handled by Stripe, and the download appears immediately afterwards in your browser. There is no account, no mailing list and no subscription.

Are the solutions included?

Yes, every volume has a complete solutions section listing each quotation, its author and the key that was used.

Can I print copies for my classroom or club?

Yes. Print as many copies as you need for your own group. Please do not redistribute the PDF itself or resell it.

This tool is free and has no account, no upload, no tracking of your text

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