The dropped third strike rule is why a batter can sometimes swing and miss, then sprint to first base. The pitch still counts as strike three, but the out is not complete until the defence finishes it.
If the rule allows the batter to run, the catcher must complete the out by tagging the batter-runner or throwing to first in time. Simply recording strike three in the count is not enough.
A pitcher can be credited with a strikeout even when the batter reaches safely on an uncaught third strike. That is how a team can record more than three strikeouts in an inning.
The catcher must legally catch the pitch in flight. A pitch that touches the ground before entering the mitt is not caught, even when the catcher controls it immediately afterward. A swinging strike that bounces, a called third strike that gets through, or a pitch lodged briefly against equipment can therefore require another defensive act. The umpire tracks the ball rather than the batter's reaction. When eligibility exists, the plate umpire may signal strike three while also indicating that the ball was not caught, and the batter-runner remains live.
Whether first base is occupied is decided when the pitch begins. A runner stealing second does not make first “open” for this rule merely by reaching second before the catcher retrieves the ball. With fewer than two outs, occupancy protects the defence from being forced into an easy extra out, so the batter is out on strike three despite the uncaught pitch. With two outs, that protection is unnecessary because retiring any forced runner can end the inning; the batter can run even when every base was occupied.
An eligible batter becomes a batter-runner and can be retired by a tag before reaching first or by a fielder holding the ball while touching first ahead of the runner. Other runners may advance at their own risk because the pitch remains live. With two outs and the bases loaded, the catcher can end the inning by stepping on home if the runner from third is forced, or by completing another available force play. The batter-runner can also give up the opportunity by leaving the dirt circle around home plate while clearly making no attempt to reach first, under the professional rule.
If the throw is late or the catcher cannot recover the pitch, the batter-runner may reach first safely while the pitcher still receives a strikeout. The scorekeeper also records the event that allowed the advance, commonly a wild pitch or passed ball, depending on whether an ordinary catcher should have controlled it. Any subsequent play proceeds with that runner legally on first. The inning therefore can continue after what the count records as strike three without treating the plate appearance as a hit.
Usually, yes. But on an uncaught third strike in the right base-out situation, the strikeout and the completed out are separate. The batter becomes a runner until the defence retires them or they reach first safely.