Bridge — and it tells you what every bid means

How to play bridge

Four players sit as two partnerships — North with South, East with West — and each gets thirteen cards from an ordinary pack. A hand of bridge is two games stacked on top of each other, and the first one is the harder one.

The auction

Starting with the dealer and moving clockwise, each player passes or bids. A bid names a number of tricks over six and a denomination: 1♠ is a promise to take seven tricks with spades as trumps, 3NT is nine tricks with no trump suit at all. Every bid must be higher than the last one, and the denominations rank ♣ < ♦ < ♥ < ♠ < NT — so 2♣ beats 1NT, and 3♠ beats 3♦. You may also double the opponents' bid, which increases both the penalty for going down and the reward for making it, and they may redouble.

When three players pass in a row the auction is over and the last bid is the contract. If all four pass at the start, the board is thrown in. Declarer is the member of the winning partnership who named that denomination first — not whoever bid last. Then the player to declarer's left leads, declarer's partner spreads their whole hand face up as dummy, and declarer plays both hands.

The whole difficulty is that partners may not tell each other anything except by bidding. So the bids carry agreed meanings, and this page shows you them: tap any bid in the box and it tells you what that bid would say, then tap it again to make it.

The play

Follow the suit that was led if you can; if you cannot, play anything, including a trump. Highest trump wins the trick, and if nobody trumps, the highest card of the suit led wins. Whoever wins leads the next one. There is no rule about breaking trumps in bridge — that is a hearts and spades rule and it is not here, and our test suite asserts the absence so nobody adds it by copying another engine.

The score

Declarer's side needs the tricks it bid plus six. Minor-suit tricks are worth 20 each, majors 30, and no trump 40 for the first and 30 after. A hundred points below the line is game: 3NT, 4♥, 4♠, 5♣ and 5♦ all reach it, which is why those are the contracts everybody aims at. Slam bonuses are 500 not vulnerable and 750 vulnerable for twelve tricks, and 1000/1500 for all thirteen. Going down costs 50 a trick not vulnerable and 100 vulnerable, and far more doubled.

What to bid, in one screen

Count your high-card points: ace 4, king 3, queen 2, jack 1. Forty in the pack, so an average hand is exactly ten.

• 0–11 — pass, unless the Rule of 20 saves you: add your points to the lengths of your two longest suits, and open if it reaches 20. Ten points with 5-5 shape is an opening bid.
• 12–21, balanced 15–17 — open 1NT. It is the most precise bid in the game and partner can place the contract almost immediately.
• 12–21, otherwise — open your longest suit, but a major promises five cards. With no five-card major open the better minor: 1♦ with four-four, 1♣ with three-three.
• 20–21 balanced — 2NT. 22 or more — 2♣, which is artificial, forcing, and says nothing whatever about clubs.
• 5–11 with a good six-card suit — a weak two. It is not a strong bid; it is an obstacle, and it works.

Then the arithmetic that decides everything: 25 or 26 combined points is game, 33 is a small slam, 37 is a grand. Almost every auction is two people trying to find out which side of those lines they are on without being allowed to say so.

The two conventions you actually need

Stayman. Partner opens 1NT and you hold a four-card major. Bid 2♣ — it asks "have you got a four-card major?" and says nothing about clubs. Partner answers 2♥ with four hearts, 2♠ with four spades, and 2♦ meaning neither.

Jacoby transfers. Partner opens 1NT and you hold five or more of a major. Bid the suit below it — 2♦ for hearts, 2♥ for spades — and partner is obliged to bid your suit. The point is not politeness: it makes the strong hand declarer, so the opening lead comes up to it rather than through it, and that is worth about a trick.

Blackwood is the third one, and it is the one people misuse. 4NT asks how many aces partner holds — 5♣ for none or four, 5♦ for one, 5♥ for two, 5♠ for three. Only ask when you already have a fit and the values for a slam, because the answer might be one you cannot survive. Its purpose is as much to stop you bidding a slam as to start you.

Honest about the bots, and about what is missing

The bidding bot plays Standard American Yellow Card, the free published system, and we measure it rather than describe it. Over 800 seeded deals bid and then played out to a score: it reaches game on 87% of the boards where the partnership holds 26 or more points and an eight-card fit; it bids game holding 22 or fewer only 9.5% of the time; 54% of the contracts it reaches make; and the mean score to the declaring side is +90. Our build fails if any of those falls below a floor.

What is in: five-card majors, better minor, 1NT 15–17, 2NT 20–21, strong 2♣, weak twos, preempts, the Rule of 20 and the Rule of 15, the one-level response ladder, two-over-one, limit raises, opener's rebid including the reverse, natural overcalls, the 1NT overcall, takeout doubles and the advances to them, Stayman, Jacoby transfers and Blackwood.

What is out, and named rather than left to be discovered: negative doubles, Jacoby 2NT, splinters, cue bids, Gerber, Roman Key Card Blackwood, fourth suit forcing, new minor forcing, two-suited overcalls like Michaels and the unusual no trump, and balancing. In an auction it does not understand the bot passes rather than inventing a meaning its partner does not share, because a bot that guesses teaches you wrong.

What the rules engine does not do: claims and concessions beyond conceding the whole hand, the penalty-card machinery, lead penalties after an established revoke, and Law 64C equity restoration, which is a director's judgement rather than an arithmetic. The revoke itself is implemented — detection, establishment and the Law 64 trick transfer — as are honours, the duplicate vulnerability cycle and the IMP scale.

And there is no live play here. Two humans with a bot partner each leaves whichever human is dummy watching for thirteen tricks, because dummy's cards are played by declarer. Four humans means one broadcast channel carrying four hidden hands that every seat's browser can read. Neither is worth shipping badly. Every other game on this site that can be played live already is; hearts and spades both seat two people against each other right now.

How we know the rules are right

Two published anchors, both derived here rather than quoted. The first is the number of possible bridge auctions: 128,745,650,347,030,683,120,231,926,111,609,371,363,122,697,557, published in closed form as (4 × 22³⁵ − 1) ÷ 3. That figure is a fact about the legality rules — how a bid must beat the last one, when a double is allowed and when it is not, that an intervening pass does not take away the right to double, and that three passes end a contract while four end a passed-out board. Our code counts the auctions its own legality function allows and reproduces all forty-eight digits. We then break each of those four rules in turn and confirm the count moves, because an anchor a broken rule still satisfies is not an anchor.

The second is the Milton Work point-count distribution. We compute the exact number of thirteen-card hands at every point total by convolving all 8,192 subsets of each suit — exact integers, no sampling — and check every published cell. That is where "twelve points is an opening bid" becomes 34.8172% instead of a rule of thumb. The scoring table is asserted cell by cell against Law 77, including the two everyone misremembers: a doubled overtrick is a flat 100 not vulnerable and 200 vulnerable whatever the suit, and the vulnerable small slam bonus is 750, not 1000.