Live betting

A new line every play

Before the game there is one line. Once it kicks off, that line closes and a live one opens. It is also called in-play or in-game betting, and it is the "live" option or tab in a betting app. There is a shorter answer at what live betting is.

The main bets are the ones you already know: who wins from here, the spread from here, the total for the whole game. Around those sit shorter markets, such as the next team to score, the result of the current drive or inning, and the total for this quarter. The team that was a 3-point favorite at kickoff and is losing by 10 at the half might now be a 4-point underdog, and that new number is the live betting line.

Nobody is typing these in by hand. A model takes the score, the time left, who has the ball and the pre-game line, and produces a price, while traders watch it and step in when something happens the model can't see, such as an injury. The line updates constantly and is taken down, or suspended, at the moments that matter: a score, a turnover, a review, a player down on the field. Then it comes back at a new number.

Where the book has the edge

Start with the price, because it is wider. Before the game a spread is usually -110 on both sides, and the book's cut is about 4.5 percent. Live lines are often -115 or -120 a side.

Price on both sides	Break-even	The book's cut
-110	52.38%	4.5%
-115	53.49%	6.5%
-120	54.55%	8.3%

Then there is the delay, and it only works one way. When you press the button, most books hold a live bet for a few seconds before accepting it, and if something happens in those seconds the book rejects the bet or offers you a new price. You don't get to take a bet back because the next play went against you.

You are also watching the past. A television broadcast runs behind the real game, and a stream on a phone runs further behind, sometimes by half a minute or more. The book's data comes from the venue much faster than that. If you are betting on what you just saw, the book already knew it.

And the limits are lower: books take less on a live line than on the pre-game line, and less still on the small markets.

None of this is spite. The book has to protect itself against people sitting in the stadium, and if I were still booking I'd do every one of those things. The result is the same for you, though. You pay more, on older information, against a price that can be pulled at any second.

Football and baseball

In live betting football, the line changes after nearly every play, and the only quiet moments are timeouts, breaks between quarters and halftime. Those breaks are when you can read a number and think about it, so that's when I'd bet, not during play.

Baseball is slower. There is time between pitches and between innings, and one event, a pitching change, can shift a game more than the score does. It suits a bettor who knows the bullpens.

When I'd use it

The best use is a better number on an opinion you already had. You liked a team before the game and it falls behind early for reasons that don't change your view (a fluke turnover, say), and the live price on that team is now better than the one you passed on. Hedging is the second: a pre-game bet or the last leg of a parlay is going well and you want to lock some of it in, and the sums are on the hedging page.

The third is something the model is slow on, like a team that has plainly changed how it is playing, or weather that turned. That is hard, and the lower limits tell you the book knows where it is weak.

Whichever it is, I'd decide beforehand what would make me bet, something like "I'll take this team if it gets to +7", and then wait for it or not bet. And I'd look at the price each time, because a live line at -120 has to win 54.55 percent of the time.

Testing an app

I'm not going to name one. For live betting, football or baseball or anything else, the things worth testing are the same:

• how long a bet sits pending before it is accepted
• how often the market you want is suspended
• what price it deals, -110, -115 or -120
• whether the live limits are large enough to matter to you

The bet that never stops asking

Live betting never stops asking you for another bet. There is a new line every few seconds, and a game that is going badly offers a way to get even on every play. That is how a $50 night becomes a $500 one, and chasing during a game does more damage than any bad opinion before it.

So set a loss limit for the game before it starts, in dollars, and stop when you reach it. A live line is still a price, and the book made it. Having a remote in your hand doesn't make it a better one.