How to solve a cryptogram

Every letter has been swapped for another, consistently. Your job is to work out the swap from the shape of the language.

A cryptogram is a sentence enciphered by substituting each letter for another, the same way throughout. Punctuation, spacing and word lengths are preserved, and that is what makes it solvable.

The method, in order

One-letter words. In English there are two: A and I. If the puzzle has a single-letter word, you have a fifty-fifty guess on the spot.

Apostrophes. Enormously informative. A letter after an apostrophe at the end of a word is almost always S, T, or the pair RE, VE or LL. "X'Y" with Y a single letter is very likely S or T.

Three-letter words. THE dominates English text. If one three-letter pattern repeats, try THE first; the payoff is three of the commonest letters at once.

Doubled letters. Only some letters double often: LL, SS, EE, OO, TT, FF. A doubled pair narrows quickly.

Frequency. Count the ciphertext letters. The most common is likely E, then T, A, O, I, N. Treat this as a hint rather than a rule — a single sentence is a small sample and can easily defy the averages.

Work in pencil, and watch for contradictions

A substitution is a one-to-one mapping: if ciphertext Q is E, no other letter can also be E. When a guess forces two ciphertext letters onto the same plaintext letter, the guess is wrong — and that is useful information, not a setback.

The cipher never maps a letter to itself

The puzzles here use a derangement, meaning no letter stands for itself. That is the traditional convention and it is a genuine solving aid: if you are considering that ciphertext H might be H, you can rule it out immediately.

Frequently asked questions

Can a letter stand for itself?

No. The puzzles use a derangement, so every letter maps to a different one. This is the usual convention and it removes possibilities as you solve.

Where do the phrases come from?

They are written for this tool rather than taken from a quotation database, so recognising the source is not a shortcut.

What if frequency analysis gives the wrong answer?

It often does on a short text — one sentence is far too small a sample for the averages to hold. Use it to rank guesses, not to decide them, and lean on word shapes instead.