Cryptogram Solver

A cryptogram is a short message encoded with a monoalphabetic substitution cipher where every letter in the plaintext is consistently replaced by a different letter throughout the message. To decode a cryptogram, you need to work out which ciphertext letter stands for which plaintext letter. There's no shift, no key, and no shared password, just an arbitrary letter-for-letter mapping that's the same throughout the message.

Cryptograms are also called cryptoquotes, cryptoquips, or substitution cipher puzzles depending on the context.

This tool decodes cryptograms two ways: paste your ciphertext and use the Solve button for an instant best guess, or work the puzzle letter-by-letter using the substitution table with frequency analysis hints. Word boundaries must be preserved (cryptoquips, in the National Puzzlers' League terminology, also called aristocrats).

How the Cryptogram Solver Works

This tool offers two complementary ways to decode a cryptogram. You can use either, or both together.

Auto-solve

Paste your ciphertext into the input field and click Solve. The solver uses statistical letter-frequency analysis combined with English-word dictionary matching to propose the most likely plaintext. It returns up to ten candidate solutions, ranked by confidence. The most likely solution will be shown first, with alternatives below in case the top guess isn't quite right. Auto-solve handles most standard cryptograms accurately, but it isn't perfect. For tricky ciphers or unusual vocabularies, the manual mode below is more reliable.

Manual mode

Below the input field, a 26-letter substitution table lets you map ciphertext letters to plaintext letters one at a time. As you type plaintext letters into the table, the decrypted text updates in real time. Alongside the table, a frequency analysis panel shows you how often each ciphertext letter appears in the message, alongside the standard frequencies of letters in English text, so you can spot likely E's, T's, and A's at a glance.

How to Solve a Cryptogram Manually

Solving cryptograms by hand is a small art — it's the cryptanalytic core of cryptography taught in introductory courses, and a fun puzzle in its own right. Here are the techniques that crack the vast majority of standard cryptograms.

Standard English letter frequencies — E dominates at 12.7%, followed by T, A, O, I, and N. In any sufficiently long substitution cipher, the most common ciphertext letter is overwhelmingly likely to stand for E.

Use letter frequency to find E, T, and A first

English letters appear in roughly predictable frequencies. The most common letters, in order, are E (12.7%), T (9.1%), A (8.2%), O (7.5%), I (7.0%), N (6.7%), S (6.3%), H (6.1%), and R (6.0%). Together these nine letters account for about 70% of typical English text. If a particular ciphertext letter appears far more often than the others in your message, it's almost certainly standing in for E. The next most common is almost always T or A. For a deeper academic treatment of letter frequency, Practical Cryptography's frequency analysis guide is the standard reference.

Look for single-letter words

In English, the only one-letter words are A and I. If your cryptogram contains a single-letter word, it's one of those two. Combine this with the frequency analysis above and you can usually pin down both A and I within seconds.

Watch for double letters

Doubled letters in English are uncommon enough that any doubled ciphertext letter dramatically narrows the possibilities. The most common doubled letters are LL, EE, SS, OO, TT, FF, RR, NN, PP, and CC. If your ciphertext contains, say, "WWRRTT," you're looking at three doubled-letter pairs, which is very rare, but useful for narrowing down which letters they might represent.

Use apostrophe patterns

Apostrophes in English mostly appear in contractions, and the patterns are highly constrained. The most useful patterns:

• X'T is almost always N'T (don't, won't, can't, isn't, …)
• X'S is almost always 'S (it's, that's, what's, …)
• X'LL is almost always 'LL (we'll, they'll, you'll, …)
• X'VE is almost always 'VE (we've, you've, they've, I've)
• X'M is almost always I'M

One contraction in your ciphertext can often unlock four or five letters at once.

Spot common short words

The most common short English words have very distinctive patterns: THE (3 letters, the most common 3-letter word by a wide margin), AND (3 letters), OF (2 letters), TO (2 letters), IN (2 letters), IS (2 letters), IT (2 letters), YOU (3 letters), THAT (4 letters, with the double-T pattern), WAS (3 letters), ARE (3 letters), FOR (3 letters), WITH (4 letters). If you see a 3-letter word that appears many times in the ciphertext, it's almost certainly THE.

Work the substitution table iteratively

As you identify letter mappings, type them into the substitution table above. Each correct mapping reveals partial words in the ciphertext, which usually suggest more mappings ("T_E" is almost certainly "THE"; "T_AT" is almost certainly "THAT"; "_OU" is almost certainly "YOU"). With practice, you can solve most cryptograms in a few minutes by hand without ever using the auto-solver.

Cryptogram puzzles make great party activities — kids can work together to crack the code using frequency analysis, pattern matching, and a bit of teamwork.

What Is a Cryptogram?

A cryptogram is a short text encoded with a substitution cipher and presented as a puzzle for the reader to decode. Each letter in the original message has been consistently replaced by a different letter (the same substitution applied throughout) and the puzzle is to work out which letter stands for which. Punctuation is usually preserved, and word boundaries are preserved in the standard cryptogram form (called a cryptoquip or aristocrat, depending on the source).

Cryptograms emerged as a popular puzzle form in the 1890s, when American "penny press" newspapers and magazines began running them as daily features. Their popularity owes a meaningful debt to Edgar Allan Poe, whose 1843 short story The Gold-Bug turned on the solving of a substitution cipher and almost single-handedly popularised cipher cryptanalysis as a recreational pursuit. Poe also wrote a non-fiction essay, A Few Words on Secret Writing (1841), that walked through the techniques.

Today, cryptograms appear daily in newspapers (the syndicated Cryptoquote by Tribune Content Agency, the Cryptoquip by King Features Syndicate), in puzzle books, in escape rooms, and in alternate-reality games. The National Puzzlers' League, the foremost cryptogram community organisation, founded in 1883, maintains formal categorisations of the various cryptogram forms (aristocrats, patristocrats, xenocrypts, and so on) and runs an active community of cryptogram constructors and solvers.

Cryptograms in Famous Puzzles and History

Substitution-cipher puzzles have a long and well-documented history beyond the daily newspaper page.

Edgar Allan Poe's 1839 cryptography challenge

In Alexander's Weekly Messenger, Poe famously challenged his readers to send him substitution ciphers, promising to solve any they could devise. He solved them all, a feat that made him one of the most famous figures in 19th-century popular cryptography. His essay A Few Words on Secret Writing and his short story The Gold-Bug together established the genre.

The Beale Ciphers (1885)

Three encrypted documents purportedly leading to a buried Virginia treasure worth tens of millions in modern terms. One of the three ciphers was decoded using a key based on the U.S. Declaration of Independence, but the other two have resisted cryptanalysis for over 130 years. Whether they're genuine, a hoax, or a flawed cipher that simply can't be solved is still debated.

The Voynich Manuscript

A 15th-century illustrated codex written in an unknown script that no one has ever decoded. Various theories have proposed it as a substitution cipher, a polyalphabetic cipher, an artificial language, or an elaborate hoax, but after more than 600 years no one has produced a verified translation.

The Zodiac Killer's Z408 and Z340

In 1969, the American serial killer known as the Zodiac Killer sent four encrypted messages to Bay Area newspapers. The first cipher, Z408, was solved within a week by amateur cryptographers Donald and Bettye Harden. The second major cipher, Z340, resisted cryptanalysis for 51 years until a team led by David Oranchak cracked it in December 2020. The FBI maintains an archive of the original ciphers.