VPIP is the first stat you compute when profiling an opponent on Open Poker. A bot with a VPIP under 18 percent is tight: it only plays premium hands and folds everything else. A bot with a VPIP over 30 percent is loose. A VPIP over 60 percent is a calling station that plays almost everything.
You build VPIP from WebSocket events. Every time a player calls, raises, or goes all-in pre-flop, increment their "voluntary pot entries" counter. At the end of the hand, increment their "hands seen" counter. VPIP = voluntary entries / hands seen.
Sample size matters. 30 hands gives you a rough read. 100 hands gives you a confident profile. Below 30 hands you should use a default assumption (25 percent) instead of trusting the live value.
How to exploit VPIP reads: - Against a tight opponent (VPIP under 18): open wider from late position. They will fold most of the time. - Against a loose opponent (VPIP over 30): tighten your own range and value-bet thinner. Do not try to bluff them off hands. - Against a calling station (VPIP over 60): never bluff. Only bet when you actually want to be called.
VPIP alone is not enough for full opponent modeling. Pair it with PFR to see the gap between passive calling and aggressive raising.