Cribbage — with the count shown

Play cribbage with friends, or with real people

Press Private room and you get a four-letter code and a link. Send either one to whoever you want to play and they are sitting opposite you — no account, no app, no email address on either side, and nothing to install. If you would rather play a stranger, Find an opponent drops you into the oldest cribbage room that is waiting; if nobody is waiting it opens one for you and seats the next person who goes looking. Live games count toward a rating; bot games do not, because a browser can lie about its own score and we would rather label that than launder it.

A dropped connection does not end the game. Refresh the page, close the laptop, lose signal in a tunnel — the same link puts you back in your own seat with the board, the pegs, the count and the history exactly where you left them. While you are away the house bot covers your turns so your opponent is not sitting in front of a dead table, and it hands the seat straight back the moment you return.

If the player who was dealing disappears, you get an honest choice rather than a fake one. Between hands you can take the deal over: every card is face up at that point, so there is nothing hidden left to inherit — you post a fresh commitment of your own and the game carries on, with the hands already played still checkable against the old one. Mid-hand you cannot, and we say so instead of pretending: the undealt pack only exists in the other person's browser, so the only options are to wait or to take the game.

A cribbage shuffle you can actually check

Every card game online gets the same accusation and gives the same non-answer. Players say the deal turns against them; operators reply that their random number generator is secure. Both can be true at once, which is exactly the problem — a secure generator says nothing about the code that decides when to call it. The complaint is unfalsifiable from your side of the screen, and that is what makes it corrosive.

So this board does not ask you to believe anything. Before a single card is dealt it publishes SHA-256 of a secret seed — the commitment — in the panel beside the board, and you supply a seed of your own. Every shuffle is a pure function of those two values and the hand number, and of nothing else: not the score, not who is winning, not whether you are one hole from the game hole. When a hand has been counted we hand you that hand's seed. When the game ends we hand you the master seed. You hash it, check it matches the commitment you were shown at the start, and re-derive the exact 52-card order and the exact six cards you were dealt. Press Check the deals and the page does it in front of you; press Copy the receipt and you get every input, every output and the twelve lines of derivation, so you can redo it in any language you like without our code in the room.

The derivation is deliberately small enough to re-implement: hash master : n to get the hand's seed, hash handSeed : yourSeed : n : counter for a stream of bytes, then run an ordinary Fisher–Yates over the numbers 0 to 51 taking each swap index from the next byte — rejecting the few values at the top of the byte range that would make low cards very slightly likelier, because 256 is not a multiple of 52 and that skew is precisely the "predictability somewhere" a suspicious player would be right to look for. A card is rank × 4 + suit. The deal comes off the top of the array: non-dealer takes deck[51], deck[49] … deck[41], the dealer takes deck[50] … deck[40], and the cut is deck[39].

In a live game both seats commit before either one opens. The dealer hashes its master seed before it can see your seed, and you hash yours before you can see the dealer's hash. Neither side can go fishing for a pair that suits them, so neither side picked this deal — that is a fact about the arithmetic, not a promise about us. Even who deals the first hand falls out of the two committed halves rather than out of somebody's coin flip.

And here is what it does not prove, because a hash that reassures without proving anything is worse than no hash at all. Against the bot the whole thing runs in your own tab — there is no server, so this proves the deal was fixed before the cut and matches the seed, and it proves nothing about a machine somewhere else. In a live game one seat derives the deck, which means that browser is holding the seed while the hand is played: the protocol proves nobody chose your cards, not that a modified opponent client could not look at them. Hiding a hand from the computer that dealt it is a different problem — mental poker — and we have not built it. The same protocol on our dice has a SHA-256 self-test against the published FIPS 180-4 vectors; it is the same hash function this page uses, so you can satisfy yourself the hash is really SHA-256 before you trust anything computed with it. That page checks dice rolls, not cards — the card derivation is checked here and from the receipt.

No cribbage app we could find offers any of this. That is not a boast about our engineering; commit-reveal is a standard trick and it has been in our dice for months. It is a statement about the state of the category: the accusation is universal and nobody has bothered to answer it with arithmetic.

How to play cribbage

Cribbage is a two-player race around a board of 121 holes. It is nearly four hundred years old, it is played with an ordinary pack, and almost all of its difficulty is in one place: counting a hand correctly. Everything below is what this board does for you automatically, written out so you can learn to do it yourself.

A hand goes like this. Each player is dealt six cards. Each throws two away face down into the crib — a fifth hand that belongs to whoever dealt. A starter card is cut from the rest of the pack; if it is a jack the dealer immediately takes 2, called his heels. Then comes the play: players alternate laying cards face up, each adding its value to a running count that may never pass 31, scoring as they go. When both hands are empty, comes the show: each player counts their four cards plus the starter, non-dealer first, then the dealer, then the dealer's crib. Deal alternates and it starts again. The first peg into hole 121 wins, and the game stops the instant it gets there — which is exactly why the counting order is a rule rather than a courtesy.

Card values, and the one thing everybody gets wrong

An ace is one, face cards are ten, everything else is its pip value. But a card has two different numbers attached to it and they are not the same number: what it adds to a count, and where it sits in a run. A ten and a jack both count ten and are not a pair. A jack, queen and king are a run of three even though they are worth thirty. And the ace is low and only low, so Q-K-A is nothing at all. Most broken cribbage scorers on the internet conflate those two numbers; ours keeps them apart deliberately and the test suite names the case.

The scoring rules, in full

Fifteens are combinations, not pairs of cards. 5-5-5 is a fifteen too, and so is 4-5-6. A hand with three fives and a ten-card contains eight separate fifteens, which is 16 points before anything else is counted.

Runs multiply. A run scores its own length once for every way of building it. Hold 4-5-5-6 and you have two runs of three — 3 × 2 = 6 — plus a pair, plus a fifteen or two. There is no separate rule for a "double run"; it falls out of counting each one.

The crib flush is the trap. Four cards of a suit in your hand is 4, and 5 if the starter matches. Four of a suit in the crib is worth nothing at all — a crib flush needs all five cards.

Runs in the play are the other trap. They are the longest tail of three or more cards that are consecutive in any order, so 5-3-4 is a run of three. A repeated rank breaks it: 8-7-7-6 scores no run, but 3-4-3-5 does, because its last three cards are 4-3-5.

And a "go" is not a turn. If your opponent cannot lay a card without passing 31, they say go — and you keep laying cards, and keep scoring fifteens, pairs and runs, until you cannot either. Only then does the last player to lay a card take 1. Reaching exactly 31 has already paid 2 and takes nothing more on top of it.

Four totals a cribbage hand can never score

A hand cannot be worth 19, 25, 26 or 27. Every other value from 0 to 29 happens. That is why a cribbage player calls a worthless hand a nineteen — it is the smallest score the game cannot produce, so naming it is a joke about counting nothing.

The maximum is 29: a jack plus the three fives of the other suits, with the fourth five cut as the starter. Eight fifteens for 16, four of a kind for 12, his nob for 1. There are exactly four such hands, one for each suit.

We are not repeating those from a pub. Cribbage is one of very few games whose entire scoring space is small enough to walk end to end: choose five cards from 52 and name one of them the starter, and there are C(52,5) × 5 = 12,994,800 scored hands. Our test suite (tools/cribbage_test.mjs) walks every one of them and records which totals ever appear, so the two facts above are checked rather than believed, and the scorer is anchored to published invariants instead of to a second opinion of its own.

Honest about the limits of that: an exhaustive proof over one part of a game is not evidence about the rest of it. Fifteen rules were deleted from the engine one at a time and the walk re-run. It caught the four hand-scoring components and none of the crib flush rule, pegging runs, pegging pairs, the 31 rule, "go", the count reset, who leads, who shows first, his heels or the 121 board. Eleven of the fifteen are held up by named unit tests instead, and we would rather say which is which.

Strategy, briefly

The discard is the decision

You throw away a third of your cards every hand, and where they go depends on who dealt. As dealer the crib is yours, so a 5, or two cards that work together like 5-5, 7-8 or a pair, is a present to yourself. As non-dealer you are arming your opponent — throw junk. The classic worst discard as non-dealer is a lone 5: it combines with every ten-card in the pack.

The crib is worth roughly four points a deal, which is most of why the deal alternates. Over a game you will deal about half the hands, so the advantage cancels, and the player who treats their non-dealer discards carelessly gives away the difference.

Fives are the whole economy

Ten-cards are sixteen of the fifty-two, so a 5 makes a fifteen with more of the pack than anything else. Keep them, and be careful about laying one during the play — a 5 that takes the count to 5, 15 or 21 hands the other player a fifteen or a 31 with any of those sixteen cards. The Hard bot here refuses to leave the count on 5 or 21 for exactly that reason.

Pegging: lead low, and do not be predictable

Leading a 4, 3 or 2 is safer than leading a 5. If they pair your lead, you may be able to make three of a kind for 6. Counting the count is most of pegging: once the total is 21 or more, the only cards that fit are small, which is when holding an ace or a 2 back pays for itself.

Position on the board matters

Late in the game the two pegs stop being decoration. If you are the non-dealer and within reach of 121, you count first and can go out before the dealer ever shows — so a hand worth eight now beats a hand worth ten next deal. That is the whole reason the counting order is fixed, and it is why the board shows both pegs.

What this board does and does not do

It plays two-handed, six-card, 121-hole cribbage — the standard game. Three- and four-handed cribbage and the five-card 61-hole variant are not implemented, and the page says so rather than letting you find out.

Muggins is not here. In some house rules, points you fail to count can be claimed by your opponent. That is a scorekeeping layer on top of correct scoring, and this board always counts every hand correctly, so there is nothing to steal. The trade is deliberate: we would rather teach you the count than penalise you for not knowing it.

What each bot level actually does

None of them search ahead. Cribbage asks a player for two decisions — a discard and a card — and that is all each level decides:

Easy throws two cards away at random and plays a random card that fits under 31. It will walk past free points. It exists so a complete beginner can finish a game.

Medium keeps the four cards with the highest score averaged over all 46 starters it cannot see — that part is exact, not sampled — and then always lays the card that scores the most right now, breaking ties towards the higher card.

Hard discards the same way but also values the crib it is feeding: it samples 220 random combinations of the two cards you might throw plus a starter, adds that figure when the crib is its own and subtracts it when the crib is yours. Its pegging is the same greedy rule with one extra preference — it will not leave the running count on 5 or 21, because either one hands you a fifteen or a thirty-one with any of the sixteen ten-cards in the pack.

The honest limit: the crib figure is sampled, not solved. An exact discard table averages over the opponent's two unknown cards as well, which is a far larger computation and one we have not done. So do not read Hard's discards as optimal. Read them as "the best four to hold, adjusted for a crib it has estimated".

Questions people ask

How do you play cribbage?

Two players get six cards each. Both throw two away into the crib, which belongs to the dealer. A starter is cut. Players alternate laying cards to a running count that may not pass 31, scoring for fifteens, pairs and runs. When the cards are gone, each hand is counted with the starter added — non-dealer first, then dealer, then crib. First to peg 121 wins, and the game stops the instant a peg gets there.

How does cribbage scoring work?

Anything adding to fifteen is 2. Each pair is 2, so trips are 6 and four of a kind is 12. A run scores one per card, once per way of making it. Four of a suit in hand is 4, five is 5, and in the crib only five counts. A jack matching the starter's suit is 1 (his nob); a jack cut as the starter is 2 to the dealer (his heels).

What is the highest possible cribbage hand?

Twenty-nine — a jack plus the three off-suit fives, cut to the matching five. Exactly four such hands exist out of 12,994,800 hand-and-starter combinations, and our suite proves it by walking all of them.

Why can a cribbage hand never score 19?

Because the components come in sizes that cannot be combined to make it. 19, 25, 26 and 27 are all unreachable; every other total from 0 to 29 occurs. Hence "a nineteen" for a hand worth nothing. Checked by exhaustive enumeration, not folklore.

What is the crib and who scores it?

The fifth hand, made from the two cards each player throws away. It belongs to the dealer and is counted last. As non-dealer you are throwing cards that will be scored against you. The deal alternates, which is what makes it fair.

What does go mean in cribbage?

That you cannot lay a card without passing 31. It is not a turn — your opponent carries on laying and scoring until they cannot either, and only then does the last card laid take 1. Hitting exactly 31 pays 2 and takes nothing extra.

Can I play cribbage online with friends?

Yes — Private room gives you a four-letter code and a link, and whoever you send it to is at the table. No account, no app, no email on either side. Find an opponent pairs you with a stranger instead: it joins the oldest room that is waiting, or opens one and seats the next person looking for a game.

What happens if someone disconnects?

The game waits for them. The same link restores your seat, the board and the pegs, and while you are gone the house bot covers your turns so nobody is stuck. If the dealer never comes back, the other player can take the deal over between hands with a fresh commitment.

How do I know the deal is not rigged?

Because you can check it rather than believe it. The hash of a secret seed is published before the deal, you add a seed of your own, the seed is handed over afterwards, and the exact shuffle re-derives from it. In a live game both seats commit before either reveals, so neither side can pick the deal. What it does not prove is set out in full above.

Is this cribbage free?

Yes. All three bot levels, live play against people, every hand, no account, no daily limit, no adverts between you and the board. Nothing here is locked and nothing is sold.