No two books agree on a price. They differ in the margin they charge, in how they react to sharp money, and in which way they shade a popular side. Betting the same game at the best of several prices is the lowest-effort, lowest-risk edge in the sport: you are not predicting anything better, you are just refusing to leave money on the table. It is also the mechanical foundation of arbitrage and positive-EV betting, both of which start with knowing every book's number at once.
You want the same side of a game. Three books have it priced differently:
Book A -115 # stake $115 to win $100 Book B -105 # stake $105 to win $100 Book C +100 # stake $100 to win $100 <- best price # Same bet, same outcome. On a $100 wager that wins: Book A payout profit: $86.96 Book C payout profit: $100.00 # ~$13 more per winning $100 bet, for zero added risk.
Across a season of hundreds of bets, always taking the +100 instead of the -115 is the difference between a break-even bettor and a profitable one. The outcome of the game never changed; only the price you locked in did.
ParlayAPI returns every book's price for a market in one call, so shopping is a single request instead of a dozen tabs. The /v1/sports/{sport_key}/odds endpoint lists each source's number per outcome, drawn from 45+ sportsbooks and sources (as of 2026-08). For live prices as they move, the WebSocket stream at /v1/ws/odds/{sport_key} pushes updates, and the top major books refresh at 2 to 4 second freshness. Sort by price, take the best, done.