Overview
Where your games stand, and whether today's cipher is still waiting for you.
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Limited accessEncode / Decode, Crack a Cipher, Auto-Solve, Analysis, Converters and the Spectrograph all work in full. The daily cipher, making games, and saved games need a free account — an email and a password is all it takes.
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Encode / Decode
Run any text through one of the six ciphers, in either direction.
Daily Cipher
One puzzle a day, the same one for everybody. It rotates at midnight UTC.
The daily cipher needs an account
Everyone gets the same puzzle each day, and whether you’ve solved it has to be stored somewhere. That’s the only reason this one is gated.
Loading today’s cipher…
Daily Cipher
Everything you need is inside — you will not have to leave this page or paste the text anywhere else.
Three checkpoints, three different kinds of cipher. Each one hands you what you need for the next, so they have to be done in order.
- The Signal — letters drawn inside a sound. Read them out of the spectrogram, then work out what they were hiding: the picture shows ciphertext, not the answer.
- The Grid — a message whose letters are all correct and all in the wrong place. Frequency analysis will tell you nothing here; the word from the signal is what unscrambles it.
- The Intercept — today’s real cipher, no key and no hints about the alphabet.
The toolbelt travels with you: fingerprinting, letter frequencies, all 25 Caesar shifts, the substitution solver and a scratchpad, always pointed at whichever checkpoint you are on. Every checkpoint has a nudge, and a full reveal if you would rather just be told.
The clock starts the moment you enter and runs on wall-clock time, so it keeps going if you close the tab. Your times are kept on this device only — nothing is sent anywhere and there is no leaderboard.
Checkpoint 1 · The Signal
spectrographThis browser will not give us a drawing surface, so the picture cannot be shown here. Everything else still works.
A nudge
Tell me outright
Checkpoint 2 · The Grid
every letter is already correctA nudge
Tell me outright
Checkpoint 3 · The Intercept
A nudge
Toolbelt
the cipher is already loadedA first guess at what kind of cipher this is, and why.
Each bar is how often that letter appears; the tick is where English would put it. A close match means the letters were not substituted, only moved.
Every Caesar shift, plus the ciphers that need no key, ranked by how much each reading looks like English.
For a substitution alphabet. This searches for the key against a model of English — it needs a good amount of text, and the daily cipher is often short enough that it will only get part of the way.
A scratchpad for working things out. It is saved on this device as you type, so it survives a reload.
Solved
Crack a Cipher
Paste ciphertext you don't have the key for. This tries every Caesar shift, the keyless ciphers, and shows you the letter frequencies — then ranks what looks most like English.
What is this?
A first guess at the cipher, from the shape of the text.
Vigenère key recovery
Splits the text into columns, solves each one as a Caesar shift, and rebuilds the keyword. Needs a decent amount of text — roughly 100 letters or more.
Keyless ciphers
These need no key, so they can be checked directly.
Every Caesar shift
25 candidatesRanked by how closely the letter distribution matches English. The top row is usually the answer, but skim the rest if it looks wrong.
Auto-Solve
For ciphers with no key and too many possibilities to try by hand. This reads the text against a model of English built from 40 million letters, and searches for the key that makes it read like a sentence.
Measured on this solver: below about 60 letters a substitution usually cannot be recovered at all, around 90 letters it gets most of it, and from 150 letters it is reliably exact. That is a limit of the cipher, not of the search — a short message simply does not contain enough evidence. The other families below need far less, because their key spaces are small enough to check exhaustively.
Best reading
The key it found
nothing pinnedEach ciphertext letter and what it was read as. A short message will leave a few letters wrong — correct one and the reading updates immediately. Pin the ones you are sure of, then search again and it will keep them fixed.
Other cipher families
These have small enough key spaces to check exhaustively, so if the text is one of them it will be at the top.
Analysis
Fingerprint a piece of text without decoding it. Letter frequencies, repeated pairs and triples, and the key-length spectrum that gives a Vigenère away.
Fingerprint
Letter frequency
Bar = this text · line = EnglishIn English, E T A O I N lead by a distance. For a substitution cipher the tallest bars are your first guesses at them. The marker on each bar is where English would sit.
Key-length spectrum
Index of coincidence when the text is split into 1, 2, 3… columns. A repeating key makes its own length spike, along with the multiples of it. Flat means there is no repeating key to find.
Kasiski examination
Repeated sequences in a Vigenère ciphertext are usually the same plaintext encrypted at the same point in the key, so the distance between them is a multiple of the key length. Factor those distances and the key length is the number that keeps dividing them. This is independent of the spectrum above — when the two agree, you can trust the answer. Note that any divisor of the real key length divides those gaps too, so if 4 and 8 both score highly the answer is probably 8.
Repeated sequences
Common English pairs are TH HE IN ER, and triples THE AND ING. Repeats that survive encryption are the cribs you build a substitution from.
Pairs
Triples
Converters
The encodings that turn up in puzzles but aren’t really ciphers — Morse, binary, hex and letter numbering.
Morse code
Letters, digits & punctuationWords can be split with / or a wide gap. Anything it
can’t recognise comes back as ? rather than being dropped quietly.
Numbers & bytes
Spectrograph
A spectrogram plots time across, pitch up, and loudness as brightness — so any picture can be read as one. Draw something, hear it, then pull the picture back out of the sound.
1. Draw
Left → right is time · up is pitchBright strokes are loud, dark is silent. Tall thin marks click; long flat lines hum. Writing a word usually comes back readable.
2. Hear it
3. Read it back
Turn the sound back into a picture. Decode what you just drew to see how much survives the trip, or open a sound file and see what is hiding in it.
Make a Game
Write a secret message, pick a cipher, and get a link. Whoever you send it to can try to crack it without making an account.
Making games needs an account
A game is saved on the server and shared by link, so it needs an owner. Whoever you send the link to still doesn’t need an account to solve it.
My Games
Everything you've made, and how people are doing against it.
Your games live behind an account
Once you’ve made a few, this is where they sit along with how many people have tried and cracked each one.
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