In a read block, blockers hold their position and watch the set and the hitter's approach before jumping, reacting to real information about where the attack is actually going rather than guessing. This is the standard approach against a team with multiple credible attacking options, since committing early to the wrong hitter can leave a blocker badly out of position and an attacker with an open lane; the tradeoff is that reading costs precious reaction time against very fast tempo attacks.
A commit block, by contrast, has a blocker jump with a specific, predetermined attacker — most often a quick-tempo middle hitter — the instant the set begins, before there is time to confirm where the ball is actually going. This sacrifices the accuracy of reading the play in exchange for a head start against attacks fast enough that reacting after the fact would otherwise be too late, and is most common specifically against a well-timed quick set to the middle.
Mixing both within a single match
Most competitive teams use a blend of both approaches depending on the situation — committing against a hitter whose quick attack has proven hard to read live, and reading against a more unpredictable offense — rather than choosing one blocking philosophy and using it exclusively for an entire match.
A third option: the release block
Between a full commit and a pure read, some teams use what is sometimes called a release block — a blocker starts by shading toward a likely quick attacker, ready to commit immediately if that attack materializes, but stays loose enough to release outward and help block a different hitter if the set instead goes elsewhere. This hybrid approach tries to capture some of the commit block's head-start advantage against the fastest attacks without fully sacrificing the flexibility a pure read block offers against a team that mixes its tempo unpredictably.
