Cipherday: three ciphers, one public-domain quote, every day

01  What Cipherday is

Cipherday is a free code-breaking game that runs in a browser tab. Each day it hands you three classic ciphers of rising difficulty. The first two hide short warm-up lines; the third and hardest hides the day's quote — a proverb, a classical saying, or a line from a long-out-of-copyright author, drawn from a bank of around two hundred public-domain lines. Crack the three stages in order and the last one decrypts into the day's reveal.

The chain is generated from the UTC date alone, deterministically and entirely inside your browser — no draw, no server deciding what you get. That is what makes the game fair: on any given day the puzzle you are looking at is the puzzle everyone else is. Puzzles are numbered, Cipherday #1 being the day the app opened.

Your streak, your best time and the chain you just cracked are kept in your own browser and nowhere else.

02  The three-cipher chain, and why it escalates

Stage one is a Caesar shift: every letter has slid the same number of places down the alphabet. There are only twenty-five shifts, which is why it is the warm-up — you turn a dial until real words appear, usually within seconds.

Stage two is a keyword substitution: every letter has been swapped for a fixed partner, so the same ciphertext letter always stands for the same plaintext letter. That consistency is the whole game — letter frequency, short words and doubled letters give you footholds, and you fill the board in tap by tap rather than guessing one value.

Stage three is where the day lives. Most days it is a Vigenère cipher: a repeating keyword shifts each letter by a different amount, so the same ciphertext letter can stand for two different plaintext letters, and the trick that breaks a Caesar outright stops working. On roughly a third of days the final stage is a rail-fence instead — a transposition rather than a substitution, where every letter is still present but re-ordered in a zig-zag across a number of rails. Which one you get is set by the same date seed.

The escalation is the point. A single-mechanic cryptogram teaches you one skill and asks you to repeat it; here a session has a shape.

03  What you actually do on screen

You work one stage at a time: ciphertext at the top of the card, a live decode line under it, and below that the control for that family plus a one-line reminder of how it works. A timer and three pips run across the top rail — locked, active, cracked.

The control changes with the family. A Caesar is a shift dial; a substitution is a board where you tap a ciphertext letter and assign it a plaintext letter, and every copy updates at once; a Vigenère is key cells you type a keyword guess into; a rail-fence is a rail count. In every case the decode line re-resolves as you move the control, so you never wait on a button to find out whether you are warm.

There is no submit button either: a stage clears itself the instant your working text matches the real plaintext — no wrong-guess penalty, no lives, nothing that sets you back. Clearing the third stage triggers a short cascade as the final layer resolves into the quote.

• The clock starts when you open the chain, and it is the number that ends up on your card.
• Stages unlock in order, so the three families arrive as three different skills.

04  Hints, and why you cannot lose

Every stage carries three ordered hints, graded on purpose: the first explains what the family is doing, the second tells you the first word, and the third is the last resort — the shift number, one cipher letter's plaintext partner, the first letter of the keyword, or the number of rails. You ask for each one, so a stuck moment costs a click rather than the day.

None of it is punished. There is no score deduction and no way to fail a day, and the nudge that appears when you have been on one stage a while says so. But the game keeps count: reach the reveal without a hint and your card says NO HINTS — the mark worth chasing, precisely because it is optional.

05  The card, the streak and the archive

Finish and you get a share card: your crack time, the three families you broke, your hint count and your streak. It never contains the quote, which is the difference between a result you can post and one you have to sit on — drop it in a group chat and everyone who has not played yet can still play.

The streak counts consecutive days: crack yesterday and today and it reads two, miss a day and it returns to one, and re-cracking today after a refresh does not inflate it. It lives in your own browser, which cuts both ways — it will not follow you to another device, and clearing site data clears it. The card can also show "faster than X% today", a comparison that only means anything because everyone solved the identical chain; when it is not available the line is left off rather than estimated.

Behind the daily is an archive of the past month of chains, one plain server-rendered page per past day: the three ciphertexts, the key for each stage, the quote it hid, and a short explanation of how that cipher worked. Today stays sealed until it becomes a past day, so nothing there spoils the current game — the page to want if you got stuck yesterday, or if you have gone looking for a specific day by its number.

06  Forging a cipher and sending it to someone

The other half of Cipherday is for people who already do this to each other by hand: pick a family — Caesar, substitution or Vigenère — write a line of up to 120 characters, and you get a link. Whoever opens it sees the ciphertext and the tools to break it, never your plaintext.

The cipher is encoded into the link itself, which is how it works with no account and nothing stored server-side: the puzzle travels in the URL. Because such a link can be edited by hand, messages are screened when the link is made and screened again on the server before the decode page renders.

07  What Cipherday deliberately does not do

It gives you one chain a day and does not pretend otherwise. No endless mode, no difficulty selector, no leaderboard, no account to climb. The archive lets you replay past days, but the streak only moves on real ones. If you want a cipher site to grind for an hour, this is not it.

There is no auto-solver, and that is a rule rather than an oversight: plenty of sites will decode a Vigenère in one click, and the point here is to do the breaking yourself. The source material is public domain on purpose — proverbs, classical sayings and pre-1929 authors, nothing in copyright.

08  Questions people ask

Is Cipherday free, and do I need an account?

Free, and no account. It is ad-supported and runs in your browser. There is nothing to install and nothing to sign up for — your streak and best time are stored in your own browser rather than on a server.

What time does the new Cipherday puzzle appear?

The chain rolls over at midnight UTC, not at your local midnight, and every player worldwide switches at the same moment. If you are in Europe or the Americas the new day usually lands during your evening or afternoon. Your streak is counted in those same UTC days, so it is worth finishing before the rollover if you are close to a milestone.

Do I need to know anything about ciphers to play?

No. Each stage shows a short reminder of how its cipher family works, every stage has three graded hints, and there is no wrong-guess penalty or failure state. Stage one is a twenty-five-option warm-up you can brute-force in seconds; the difficulty curve is the game.

Can I play a past Cipherday I missed?

Yes. The archive holds the previous month of chains, one plain page per day, and you can open any of them and work the ciphers. Those pages also publish the keys and the revealed quote, which makes them the place to look if you want to check a specific day — the current day stays sealed until it becomes a past one.

Does sharing my result spoil the puzzle for other people?

No. The card carries your time, which ciphers you cracked, your hint count and your streak — never the quote and never any of the ciphertext. Someone who has not played yet can look at your card and still play the day themselves.

Is there a Cipherday answer or solver?

The archive publishes the full chain, the keys and the quote for past days, so a day you already missed can be looked up. For today there is no published answer and no auto-solver built in — the intended route out is the three graded hints on each stage, which get you moving without solving it for you.

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