Arb betting or simply “arbing” is the process by which gamblers attempt to find anomalies in the odds offered by bookmakers and/or betting exchanges on markets to guarantee a profit no matter what the outcome of an event may be.
Arb bets are sometimes called “surebets” or “miraclebets”. The opportunities for arb betting usually arise because bookmakers and/or exchange betting markets have different opinions on the likely outcomes of an event, or simply due to bookmaker error. In most cases, arb betting will involve the use of betting with two or more bookmakers or exchanges on the same event(s). So, to be successful, gamblers need to find bookies or exchanges offering different odds on the same event.
Mathematically speaking, the opportunity for successful arbitraging occurs when the odds representing all conceivable outcomes’ probabilities total less than one. So, with a tennis match, for example, with only two possible outcomes, if you could hypothetically bet on player A at better than even money with one bookmaker, and player B at better than even money with another bookmaker, you would guarantee a profit no matter which player won.
The advent of exchange betting makes arb betting a more realistic prospect for UK gamblers thanks to the ability to lay bets. If a gambler spots odds with a bookmaker for a horse in a race at 10-1 but is able to more or less simultaneously lay the same horse at, say, 8-1 with a betting exchange, then s/he is guaranteed not to lose money and may win two times his or her stake (less the exchange’s c.5% commission) should the horse win.
Similarly, if a selection moves significantly in the market, gamblers may take advantage of price fluctuations to guarantee a no-loss and potential win. In these cases, arb betting is similar to hedging one’s bets. In some cases, arb gamblers will gamble on every possible outcome (as with the previous tennis example) to guarantee a profit whatever happens.
Generally speaking, arb betting usually offers small percentage returns, but those returns are, of course, guaranteed if arbing opportunities can be found. Such opportunities aren’t easy to find and often don’t last for long, so arb gamblers often have to be quick on the draw, but also to be patient for the opportunities to come along and for the generally small percentage gains they offer.