After the Supreme Court cleared the way for states to legalize sports betting, daily fantasy sports companies like FanDuel and DraftKings got to work immediately. Why? Sports gambling will account for a huge chunk of their business.

Ironically enough, both companies have long argued that daily fantasy sports, in which users can win cash prizes in exchange for cash entry fees, is legal because it’s technically a game of skill, not a game of chance.

Annually, illegal sports betting amounts to an approximately $150 billion industry, and DraftKings isn’t waiting until the fall to start taking bets from its users. Though DraftKings plans to officially launch its sportsbook right on time for NFL season, it gave Fortune an early glimpse. At this time, the DraftKings Sportsbook online version and mobile app will be available for an invite-only period that gives users a chance to gain early access by registering on its website. People will only be able to place bets and see the product if they are physically located in the state of New Jersey.

DraftKings Sportsbook product lead Dan Hannigan-Daley gave Fortune a demo of the new app. He explained that the team began working on the project roughly a year ago — before the Supreme Court decision was announced.

Hannigan-Daley said he expects the majority of DraftKings’ existing users to download its sportsbook offering because “75% of our users are already betting on sports in some capacity, according to our research.” DraftKings has been testing the app internally for the last month.

To place a bet, a user would open the app, select the outcome of a game, put in the wager amount, and place the bet. At any point, the user can see his open wagers and cash out at any time during or after the game.

Courtesy of DraftKings

When asked about some of the competitors who also offer sports betting, Hannigan-Daley said DraftKings has built a product that’s of a caliber similar to “the more sophisticated sportsbooks in the U.K.” There are a number of local state betting offerings that don’t have the breadth or depth of DraftKings Sportsbook, he said.

But its closest rival is daily fantasy sports company FanDuel, which recently agreed to be acquired by Ireland-based gaming company Paddy Power Betfair. Though FanDuel has not debuted its sportsbook yet, it also plans to officially launch before football season.

The historic ruling will intensify the competition between the two daily fantasy companies as they rush to bring their new products to market. As you may remember, DraftKings’ proposed merger with FanDuel unraveled last summer over antitrust concerns, which meant both companies had to operate as competitors — again. Now, DraftKings will need to play bigger and more defensively as FanDuel has the backing of a large, global sports betting operator.

NFL season is bound to be much more interesting this time around.