When a player is faced with a current bet amount that he has insufficient remaining stake to call and he wishes to call (he may of course fold without the need of special rules), he bets the remainder of his stake and declares himself all in. He may now hold onto his cards for the remainder of the deal as if he had called every bet, but he may not win any more money from any player above the amount of his bet. In no-limit games, a player may also open the betting by going all in, that is, betting his entire stack.

A player who goes "all-in" effectively caps the main pot; the player is not entitled to win any amount over his/her total stake. If only one other player is still in the hand, the other player simply matches the all-in (retracting any overage if necessary) and the hand is dealt to completion. However, if multiple players remain in the game and the bet rises beyond the all-in's stake, the overage goes into a side pot. Only the players who have contributed to the side pot have the chance to win it. In cases of multiple all-in bets for varying stakes, multiple side pots will need to be created.

For example, with three players in a game, Player A, with a large stack, opens the betting round for $20. Player B only has $10. She calls the $10, going all in. Player C has $30, and thus can either call the full $20, re-raise to $30, or fold. Player C decides to "re-raise all-in" by betting his remaining stake. The bet is now $10 to Player A, who calls. Player A is the only player at the table with a remaining stake; he may not make any further bets this hand. Because Player B can only win $10 from each of the other two players' $30 bets, that $10 is taken from all players' bets and the $30 total is placed in the main pot. The $40 remaining, for which Players A and C are separately contesting, goes in a side pot. As no further bets can be made, the hand is now dealt to completion. It is found that Player B has the best hand overall, and wins the main pot. Player A has the second-best hand, and wins the side pot. Player C loses the hand, and must "re-buy" if he wishes to be dealt in on subsequent hands.

There is a strategic advantage to being all in: a player cannot be bluffed, because he is entitled to hold his cards and see the showdown without risking any more money. Opponents who continue to bet after the player is all in can still bluff each other out of the side pot, which is also to the player's advantage since players who fold out of the side pot also reduce his competition for the main pot. But these advantages are offset by the disadvantage that the player cannot win any more money than his stake can cover when he has the best hand, nor can that player bluff other players on subsequent betting rounds when he does not have the best hand.

Some players may choose to buy into games with a "short stack", a stack of chips that is relatively small for the stakes being played, with the intention of going all in after the flop and not having to make any further decisions. However, this is generally a non-optimal strategy in the long-term, since the player does not maximize his gains on his winning hands.

All-in before the deal Edit

If a player does not have sufficient money to cover the ante and blinds due, that player is automatically all-in for the coming hand. Any money the player holds must be applied to the ante first, and if the full ante is covered, the remaining money is applied towards the blind.

If a player is all in for part of the ante, or the exact amount of the ante, an equal amount of every other player's ante is placed in the main pot, with any remaining fraction of the ante and all blinds and further bets in the side pot.

If a player is all in for part of a blind, all antes go into the main pot. Players to act must call the complete amount of the big blind to call, even if the all-in player has posted less than a full big blind. At the end of the betting round, the bets and calls will be divided into the main pot and side pot as usual.

For example, Alice is playing at a table with 10 players in a tournament with an ante of $1 and blinds of $4/$8. Alice is due the big blind but she only has $8. She must pay the $1 ante and apply the remaining $7 towards the big blind, and she is all in. Bob, next to act, calls $8, the full big blind amount. Carol raises to $16 total. All remaining players fold, the small blind folds, and Bob folds. The amount in the main pot is $10 (the sum of all antes) plus the full $4 small blind since Alice had this amount covered, plus $7 from Alice and every other player who called at least that amount, namely Bob and Carol. The main pot is therefore $10+$4+$21=$35. The side pot of $10 ($1 in excess of Alice's all-in bet from Bob, and $9 in excess of Alice's all-in bet from Carol) is paid immediately to Carol when Bob folds.