Condition — Prone

You are lying on the ground, either knocked down or voluntarily dropped.

Mechanical Effects:

• You are Off-Guard (-2 circumstance penalty to AC)
• You take a -2 circumstance penalty to attack rolls
• You can only Crawl (move 5 feet) or use the Stand action (1 action to get up)
• You gain +4 circumstance bonus to AC vs. ranged attacks if you Take Cover while Prone
• Melee attacks against you are unaffected (or easier due to Off-Guard)

How Applied:

• Trip action (Athletics vs. Reflex DC)
• Critical failures on certain checks
• Falling
• Some spells and monster abilities
• Voluntarily dropping Prone (free action)

How Removed:

• Stand action (costs 1 action, triggers reactions like Attack of Opportunity)
• Being pulled to your feet by an ally

Interactions:

• Prone + ranged defense: Dropping Prone and Taking Cover gives +4 to AC vs. ranged attacks — a legitimate defensive tactic against archers
• Prone creatures are easier to Grapple (they're already on the ground)
• Standing from Prone triggers Attack of Opportunity from adjacent enemies with that reaction

Tactical Impact: Trip is one of the best martial actions in PF2e. Prone makes the target Off-Guard (-2 AC) for the rest of the party, and Standing costs them an action (plus triggering AoO). Athletics-focused characters should Trip frequently.