If both players pass priority in succession does every spell and ability on the stack resolve at once?

When both players pass priority in succession without anyone taking an action, only the topmost spell or ability on the stack resolves — not the entire stack at once. This is governed by CR 117.4 and CR 608.1.

After that single item resolves, the Active Player (the player whose turn it is) receives priority again (CR 117.3b). Both players must pass priority again before the next item on the stack can resolve. This process repeats until the stack is empty, at which point the game returns to the appropriate step or phase.

This is important because either player can respond after each resolution. If a spell resolves and creates a new game state — like destroying a creature — each player gets a window to cast spells or activate abilities before the next item resolves.

Example: You cast Lightning Bolt targeting your opponent, and they cast Counterspell targeting it. The stack has Counterspell on top of Lightning Bolt. Both players pass priority — Counterspell resolves and counters Lightning Bolt. The stack is now empty; Lightning Bolt does NOT then resolve. Both items did not resolve simultaneously.

So the golden rule is: one item resolves per round of passed priorities, and players always get a chance to respond in between resolutions (CR 117.4, CR 608.1).