4-bet

The fourth preflop bet (a raise of the 3-bet)

Definition

The 4-bet is the raise of the preflop 3-bet. It's a very strong action that drastically narrows the range played. A 4-bet represents either ultra-premium hands (AA, KK, sometimes QQ and AKs for value), or well-chosen bluffs with blocker effects. The 4-bet range must be polarized to be unexploitable: best hands + bluffs, with no medium hands. The most effective 4-bet bluffs are hands that block the opponent's premium combos (A5s blocks AA and AK) and have little value as a call (so you may as well bluff). Facing a 4-bet, the decision is usually binary: fold or all-in (5-bet jam). Calling a 4-bet with a deep stack is generally suboptimal because you play OOP with an unbalanced range. The standard 4-bet size is roughly 2.2x to 2.5x the opponent's 3-bet in position, and up to ~2.8x out of position.