A sportsbook is a business — online or physical — that accepts bets on sporting events. They're the platform where you place bets and collect winnings if your bets win.
How Sportsbooks Work
Sportsbooks set odds on events and accept wagers from customers. Their core business model:
Set odds: Oddsmakers calculate the probability of each outcome and price odds accordingly — with a built-in margin (the vig).
Accept bets: Customers deposit money and place bets at the posted odds.
Settle bets: After the event, winning bets are paid out and losing bets are collected.
Profit from the margin: Regardless of who wins, the sportsbook profits from the vig on all bets — provided they've achieved relatively balanced action on both sides.
The Balanced Book Ideal
Sportsbooks try to achieve "balanced books" — equal amounts wagered on both sides of every bet. When books are balanced:
- The winning side gets paid from the losing side's stakes
- The sportsbook keeps the vig from both sides as profit
- No exposure to the outcome (they win either way)
In practice, books are rarely perfectly balanced. They manage risk by moving lines to attract action on whichever side is short, and by limiting bets from sharp bettors who consistently find value.
Types of Sportsbooks
Recreational/retail books: DraftKings, FanDuel, BetMGM, Caesars. Designed for casual bettors. Offer promotions, extensive interfaces, limit winners.
Sharp/professional books: Pinnacle, CRIS, Bookmaker. Accept large sharp bets, have lowest margins, don't restrict winners. Their efficient lines set the market benchmark.
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