Code Break Tips: Crack the 4-Digit Code Without Wasting Your 10 Guesses (2026)

1. Probe with four different digits

Make your first guess four distinct digits — 0123, 1478, anything like that. The reason is the scoring rule itself: a digit of the secret is credited at most once, so a probe built from four different digits gives you an unambiguous answer. Every bull names a digit sitting in that exact position, every cow names a digit that is in the code but somewhere else, and the two can never be confused. Measured across 500 random codes, a guess of 0123 always returned bulls plus cows equal to the number of those four digits that were actually in the secret — zero exceptions.

A distinct-digit probe also settles the leading digit for free. If you open with 0123 and the first digit comes back 0 bulls, then either 0 is not in the code at all or it is not in the first place, and the rest of the answer tells you which of the two it is.

2. No bulls and no cows is your strongest elimination

When a guess comes back with nothing at all, none of its digits are in the code. That was confirmed on every zero case the harness saw: of 500 random probes, 63 returned 0 bulls and 0 cows, and in all 63 none of the probe's four digits appeared anywhere in the secret. With four distinct digits, one guess therefore deletes four candidate digits from the pool, which is the fastest way to shrink it.

Hunt for this signal early. A guess of 0000 that returns nothing has proven that zero is absent, and it cost you one of ten. A guess that returns bulls and cows has only told you where a digit sits.

3. A cow names the digit, not the place

A cow means one specific thing: this digit is in the code, and it is not in the position you guessed. The measured example is clean — the guess 0011 against the secret 1234 returns 0 bulls and 1 cow, so the digit 1 is in the code but not in the fourth place. What the cow does not tell you is how many copies of that digit there are, because roughly half of all codes repeat a digit (section 6).

Keep the information in two separate columns: a set of digits you know are in the code, and a set of positions you know are still open. A cow fills the first column and clears one cell of the second. When the columns get short, you are close to an answer, and section 5 explains how to spend the remaining guesses.

4. Never probe with a repeated digit

The rule that makes the game interesting also makes repeated probes useless. Guessing 1111 against the secret 1212 returns 2 bulls and 0 cows: the two extra 1s earn nothing, because the secret's digits are credited at most once. A repeated probe can never tell you that the code holds three 1s, and it still burns one of your ten guesses.

Repeated digits belong in the final answer, when you already know the digit and are testing where it goes. They have no place in a probe.

5. Spend the ten guesses in two phases

Phase one, probe. Use distinct-digit guesses to find out which digits are in the code. With four positions, ten digits each, and every position drawn independently from the ten digits (measured: over 2,000 draws each position produced all ten digits), there are 10,000 possible codes and each guess returns only one bulls-and-cows pair. Guessing blind cannot catch that; information can.

Phase two, commit. Once the digit set is known, start placing the confirmed digits in candidate positions. Each commit that returns a bull fixes that position, and each that returns a cow moves that digit to a different slot. Two habits keep the budget: never repeat a guess you have already made — the build accepts it, records it in the history and charges it to your ten, while the counts it returns are recomputed from the same rule and tell you nothing new — and keep your last guess for your best complete answer, because the round ends the moment the tenth wrong guess lands.

6. Plan for repeated digits and for a leading zero

Two measured facts change how you probe. Close to half of the codes repeat a digit: 964 of 2,000 sampled codes, 48 percent. So never assume a digit occurs exactly once — a cow leaves the count open, and the second copy is often the reason a nearly-finished guess fails.

And the code can start with 0: 190 of 2,000 sampled codes did, about 9.5 percent. A mental model of "the first digit is 1 to 9" is wrong roughly one time in ten, and it will cost you the whole round when it happens. A probe that includes 0 in the first slot covers the case for free.

7. Drill a specific code with ?code= and ?seed=

The build takes two query parameters, both verified on the live game. ?code=0421 pins that exact code — the build accepts any four-digit value, including one that starts with 0, and 0421 is a legal secret. ?seed=playnesta replays the same random code every time: the same seed produced 1312 on two separate loads, while a different seed produced 6816. An invalid ?code=12 is ignored and the round falls back to a random draw.

Use these as practice tools. Pin a code with a repeat (?code=1122) to drill the "where does the second copy go" question, and re-run a seed you could not crack to see whether you read the counts correctly the first time. The round also keeps your wins, losses, streak and best streak in this browser only, and it publishes no average solve time and no comparison with other players — so there is no scoreboard to chase, only the code in front of you.

FAQ

How is this different from the rules on the game page?

The game page explains how to operate: type or tap four digits and submit, read the bull and cow counts of your last guess in the history list, use Backspace and Enter, watch the counter in the top right, and add ?code= or ?seed= to the URL. This guide assumes you know that and plays the layer above it: which probe to send first, how to read a zero, what a cow does and does not tell you, when to start committing positions, and how to spend ten guesses against 10,000 possible codes. Read the rules on the page, then work the strategy here.

What does "0 bulls and 1 cow" actually tell me?

That the digit is in the code and is not in the position you guessed — nothing else. It does not tell you which of the other three positions holds it, and it does not tell you whether the code holds one copy of that digit or two. The measured example is 0011 against 1234: the digit 1 is in the code, just not in the fourth place.

Why does guessing 1111 against 1212 only give 2 bulls?

Because a digit of the secret is credited at most once. The two 1s in positions one and three are bulls; the other two 1s in your guess find no unmatched copy of 1 left in the secret, so they score nothing. The rule is the same one that makes 3311 against 1233 return 3 cows instead of 4.

Is there a way to know how many guesses a code should take?

No, and this build does not pretend otherwise. There is no par, no hint button and no difficulty setting: the code is drawn at random, the round is ten guesses, and the page stores only your own wins, losses and streak in this browser. It publishes no average solve time, so any "most people crack it in five guesses" figure you read elsewhere is not something this page can back. What this build does give you is the two practice parameters in section 7.

Can the code start with 0, and can a digit repeat?

Both, and both were measured on the live build: 190 of 2,000 sampled codes started with 0, and 964 of 2,000 repeated a digit. The build's own ?code=0421 pin confirms a leading zero is a legal secret.

What happens on the tenth wrong guess?

The round ends, the secret is revealed, and the game stops accepting input — a key press after that point does nothing. The history still shows all ten guesses with their counts, which makes the tenth guess the most useful one to learn from.

Where can I play it?

Right on this site's Code Break page. The mechanic — guess a four-digit secret in ten tries and read bulls and cows after every guess — has no single author, so this build is written from scratch by Playnesta with no byte-reused game files: the engine (js/main.js: the splitmix32 seeded draw, the bulls-and-cows rule where a secret digit is credited at most once, the ten-guess round, the guess history, the on-screen keypad and the rules modal), the stylesheet, the analytics bridge and the touch shim are all Playnesta-original (MIT, see LICENSE.txt in the package). The closest upstream project found during selection, maxwellito/breaklock @ 8dedd3b (MIT), was read as a mechanism reference only — no bytes are copied and no file under its licence is redistributed; its webpack and babel build chain was also far heavier than this shell allows. The classic four-digit code-breaking board game this genre comes from is sold under a registered brand name; that name appears here only as a tag and a search phrase, never as the game's name, slug or title. Playnesta Games is the developer and publisher of this web implementation.