Write it in a cipher.
See who can read it.
Six classic ciphers, a daily puzzle, and a workbench that cracks the ones you don’t have the key for. Then hand a friend a link and see how they do.
Free account — email and password, nothing else. Or use the workbench as a guest, with no account at all.
Three steps from a secret to a shared link
Nothing to install. You write the message, we handle the encoding, your friend gets a link.
Pick a cipher
Six to choose from. Some take a key you invent yourself, others work straight out of the box.
Write your message
The ciphertext builds as you type, so you can see exactly what your friend will be staring at.
Send the link
They open it and start guessing. No sign-up on their end, and you can watch the attempts add up.
What you get
All of it sits in one workspace, and all of it is free.
Six classic ciphers
Caesar, Vigenère, substitution, Atbash, ROT13 and Base64, in either direction, with a live preview as you type.
A new cipher daily
One puzzle a day, the same one for everybody, rotating at midnight UTC. Crack it and the next is waiting tomorrow.
Games for your friends
Lock a message with a key only you know and share the link. Solving it needs no account, and you can see who got there.
Crack what you can’t read
Paste ciphertext with no key. It fingerprints the cipher, brute-forces every Caesar shift, and recovers Vigenère keywords on its own.
Draw a sound
The spectrograph turns a drawing into audio that hides the picture, and pulls pictures back out of sound files.
Analysis and converters
Letter frequencies, repeated pairs, the key-length spectrum — plus Morse, binary, hex and letter numbering.
A workbench, not just an encoder
Anyone can shift letters by three. The useful part is what you reach for when you have the ciphertext and nothing else.
You can use all of this without an account
Cracking, analysis, the converters and the spectrograph all run as a guest — nothing to sign up for, nothing to confirm. Only the daily puzzle and the games you save need an account, because those have to remember who you are.
It works out the cipher for you
Auto-detection reads the shape of the text and tells you what it is looking at, and why. Every Caesar shift is ranked by how much it reads like English, Vigenère keywords are recovered from the ciphertext alone, and a substitution alphabet you were never given gets searched out against a model of English built from 40 million letters.
AOL WHJRHNL PZ BUKLY AOL IYPKNL
The statistics that give a cipher away
Letter frequencies against what English would do, the pairs and triples that survive encryption, a key-length spectrum that spikes at the length of a repeating key, and a Kasiski examination that confirms it from the gaps between repeats.
Hide a picture inside a sound
Draw on a canvas and it becomes audio whose spectrogram is your drawing. Play it, save the wav, or point it at any sound file to see what its spectrogram has been hiding.
The cipher set
From a shift a child could break to a substitution alphabet that will genuinely take a while.
Today's cipher is already waiting
Make an account and it's the first thing you'll see. Then go write something nobody else can read.