A sportsbook is a gambling establishment that accepts bets on the outcome of sporting events. It used to be a niche industry, but now it is legalized in more than 20 states. In order to operate a sportsbook, you must be familiar with state regulations and follow responsible gambling practices. You must also understand the nuances of the industry and be prepared for heavy losses.

The betting market for a Sunday NFL game begins to take shape almost two weeks before kickoff. A handful of sportsbooks will release the so-called “look ahead” lines, which are based on the opinions of a few smart sportsbook managers. Then, late on the day before the game, those same sportsbooks will re-release the look ahead odds after making adjustments based on action from sharps.

Retail sportsbooks walk a fine line between driving as much volume as they can while maintaining their margins. They have to be careful not to attract too many customers from the wrong crowd — that is, those who have more information about their markets than they do. This information may not be insider tips about players or coaches but rather simple market data like who is beating them, when they’re getting beat and why.

To combat this problem, most retail sportsbooks offer relatively low betting limits and heavily curtail their customer base. They may even use geo-location to make sure that a bettor is in an unrestricted state.