Instant replay began as a way to improve call accuracy and league credibility.

Early use focused on binary rulings like buzzer-beaters and three-point foot-on-the-line, later expanding to flagrant levels, out-of-bounds, and timing.

The league, broadcasters, and vendors built a central replay hub using multi-angle HD and frame-by-frame checks to reduce errors.

Replay can slow rhythm briefly, but in playoff intensity it reduces irreversible damage from disputed calls.

Rules evolved: what’s reviewable, challenge limits, and the roles of refs and the center clarified.

The tradeoff favors fairness over pace—modern NBA spends time to get key calls right, honoring players’ effort and teams’ stakes.