What Does Passive Perception Show You?

Perception can be a weird skill to use, particularly passive Perception. Jeremy Crawford describes passive Perception as a "floor" for active Perception. It represents the minimum a character perceives just walking around. Some characters have very high passive Perceptions, particularly if they take the observant feat. This gives the impression that they can see just about every secret door or spike trap without having to look around at all.

Here's a trick for giving characters the benefits of a high passive Perception without revealing everything all the time. A high passive Perception reveals something, but it doesn't have to reveal everything.

As an example, a character with a 16 passive Perception walks into an old crypt chamber. There's a secret door over on the western wall of the crypt requiring a DC 14 Wisdom (Perception) check to detect. Our perceptive character notices some of the cobwebs are moving over by the wall where there shouldn't be any airflow. Now, when we reveal this to the players, they know there's something going on over there. They just don't know what. They can roll Wisdom (Perception) or Intelligence (Investigation) checks if they want to learn more, finding the secret door and its mechanisms by beating a 14, or they can talk their way through their investigations, eventually learning about the secret door.

In another example, the characters walk through the hall of a sundered castle now being used as a headquarters for hobgoblins. A character with a passive Perception of 14 is up front. Without a roll, they may see that some of the tiles in the hallway up ahead are cleaner than the others, maybe they've been replaced or manipulated in some way. A deeper intelligence (Investigation) check gives the character more information on how the trap works and what to avoid but that initial passive Perception gives them the clues they need to choose their next actions.

For more on running traps, see the Flow of Trap Detection.

Passive checks give characters some sense of what's going on but it doesn't have to reveal the whole thing. This makes passive checks still useful without making them so powerful that there's almost no reason to roll.

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