Can your opponent gain priority and respond during your declare blockers step?

During the Declare Blockers Step, the defending player declares all blockers simultaneously. Once blockers are declared and the game checks that all blocking restrictions and requirements are met, the active player receives priority first, then the non-active player — meaning both players have the opportunity to cast instants, activate abilities, or take other priority actions before the game moves on (CR 509.4, CR 509.5).

This window is extremely important strategically. Common plays during this step include casting pump spells to survive combat, using removal to kill a blocker before damage, or activating creature abilities that affect power and toughness. Because this happens before combat damage is assigned, those effects fully influence the damage step (CR 116.3).

Priority passes back and forth until both players pass in succession with an empty stack. Only then does the game move to the Combat Damage Step (CR 116.4). Neither player can skip this window unilaterally — both must pass priority consecutively.

Example: You attack with a 2/2 and your opponent blocks with a 2/2. Before combat damage, you cast Giant Growth (targeting your attacker) making it a 5/5. Your opponent then responds by casting Shock on your creature. These spells resolve in last-in-first-out order: Shock resolves first dealing 2 damage to the 2/2 (making it 2/2 with 2 damage), then Giant Growth resolves making it a 5/5 with 2 damage marked, which survives combat.

This priority window also exists after first-strike damage if any creature has first strike or double strike, giving players another chance to respond before regular combat damage (CR 510.5).