Range checking is the process of evaluating whether a player’s bets and actions on each street are logically consistent with the hand range implied by their pre-flop actions. A player who raises from UTG and then bets every board is implicitly representing a very strong range. Verifying range consistency is essential for detecting bluffs and understanding when to give credit to an opponent’s story. Modern solvers show that ranges represented on different streets must logically overlap for a strategy to be defensible.